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Handeling errors in Python requests [duplicate]

This question already has answers here:
Python requests.exceptions.SSLError: EOF occurred in violation of protocol
(9 answers)
Closed 1 year ago.
I am learning to use requests in Python and I need a way to get a meaningful output if the site does not exist at all.
I looked at this question, but it is unclear if the OP of the question actually wants to check if the site exists, or if it just returns an error. The problem with all of the answers that question is that if the site does not exist at all we cannot really use HTTP response headers, because no response is returned from a server that does not exist.
Here is an example.
If I use this code I will not get any errors because the site exists.
import requests
r = requests.get('https://duckduckgo.com')
However, if I enter a web page I know does not exist I will get an error
import requests
r = requests.get('https://thissitedoesnotexist.com')
if r.status_code == requests.codes.ok:
print('Site good')
else:
print('Site bad')
This error is super long and I would prefer to have a more meaningful and short error if the site does not exist.
Traceback (most recent call last):
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\connectionpool.py", line 699, in urlopen
httplib_response = self._make_request(
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\connectionpool.py", line 382, in _make_request
self._validate_conn(conn)
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\connectionpool.py", line 1010, in _validate_conn
conn.connect()
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\connection.py", line 416, in connect
self.sock = ssl_wrap_socket(
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\util\ssl_.py", line 449, in ssl_wrap_socket
ssl_sock = _ssl_wrap_socket_impl(
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\util\ssl_.py", line 493, in _ssl_wrap_socket_impl
return ssl_context.wrap_socket(sock, server_hostname=server_hostname)
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\ssl.py", line 512, in wrap_socket
return self.sslsocket_class._create(
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\ssl.py", line 1070, in _create
self.do_handshake()
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\ssl.py", line 1341, in do_handshake
self._sslobj.do_handshake()
ssl.SSLEOFError: EOF occurred in violation of protocol (_ssl.c:997)
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\requests\adapters.py", line 439, in send
resp = conn.urlopen(
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\connectionpool.py", line 755, in urlopen
retries = retries.increment(
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\urllib3\util\retry.py", line 574, in increment
raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='234876.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:997)')))
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\Users\ADMIN\Desktop\tetst.py", line 2, in <module>
r = requests.get('https://234876.com')
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\requests\api.py", line 75, in get
return request('get', url, params=params, **kwargs)
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\requests\api.py", line 61, in request
return session.request(method=method, url=url, **kwargs)
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\requests\sessions.py", line 542, in request
resp = self.send(prep, **send_kwargs)
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\requests\sessions.py", line 655, in send
r = adapter.send(request, **kwargs)
File "C:\Users\ADMIN\AppData\Local\Programs\Python\Python310\lib\site-packages\requests\adapters.py", line 514, in send
raise SSLError(e, request=request)
requests.exceptions.SSLError: HTTPSConnectionPool(host='234876.com', port=443): Max retries exceeded with url: / (Caused by SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:997)')))
Is it possible to make a function that returns, for example print('The site probably does not exist') or at least does not give an EOF error?

Normally the desirable thing to do is trap Exceptions from requests
You also can use .raise_for_status() on the Response to get a meaningful Exception for non-OK requests
However, you want to watch out for where you want to handle an Exception
immediately? can your program handle it meaningfully or should it exit?
should the caller handle a specific Exception (such as requests.exceptions.Timeout) or a more general one?
do you have many functions which call each other? should any handle some subset of possible Exceptions? and which?
See Python Exception Hierarchy for how the first-party Exceptions inheritance structure
import sys
import requests
def some_function_which_makes_requests():
r = requests.get("https://example.com", timeout=(2,10))
r.raise_for_status() # raise for non-OK
return r.json() # interpret response via some method (for example as JSON)
def main():
...
try:
result_json = some_function_which_makes_requests
except requests.exceptions.Timeout:
print("WARNING: request timed out")
result_json = None # still effectively handled for later program?
except requests.exceptions.RequestException as ex:
sys.exit(f"something wrong with Request: {repr(ex)}")
except Exception:
sys.exit(f"something wrong around Request: {repr(ex)}")
# now you can use result_json

Did some more research and just learned that I need to use a Python Try Except as mentioned by #Anand Sowmithiran. Here is a video explaining it for beginners: https://www.youtube.com/watch?v=NIWwJbo-9_8
import requests
try:
r = requests.get("http://www.duckduckgo.com")
except requests.exceptions.ConnectionError:
print('\n\tSorry. There was a network problem getting the URL. Perhaps it does not exist?\n\tCheck the URL, DNS issues or if you are being rejected by the server.')
else:
print(r)

Python http requests.exceptions.ConnectionError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))

I'm writing a chat program. Each of my clients has an open get request to the server in a separate thread (and another thread for posting their own messages). I don't want to have a lot of overhead. That is, clients don't send get requests frequently to see if there have been any unseen messages. Instead, they always have exactly one open get request to get the new messages, and as soon as the server responded to them with new unseen messages, they immediately send another get request to the server to stay updated and so on.
So on the client-side, I have something like this:
def coms():
headers = {'data': myAut.strip()}
resp = requests.get("http://localhost:8081/receive", headers=headers,timeout=1000000)
print(resp.text)
t = threading.Thread(target=coms, args=())
t.start()
On the server-side, I have something like this:
def do_GET(self):
if self.path == '/receive':
auth=self.headers['data']
#Using auth, find who has sent this message
u=None
for i in range(len(users)):
print(users[i].aut,auth)
if users[i].aut==auth:
u=users[i]
break
t=threading.Thread(target=long_Poll,args=(u,self))
t.start()
and
def long_Poll(client,con):
while True:
if len(client.unreadMessages) != 0:
print("IM GONNA RESPOND")
con.end_headers()
con.wfile.write(bytes(client.unreadMessages, "utf8"))
client.unreadMessages=[]
break
con.send_response(200)
con.end_headers()
And the logic behind this is that the servers want to do the long-polling, that is, it keeps GET/receive requests open in another busy-waiting thread. When any client sends a message to the server via POST/message it just adds this new message to other clients unseenMessages and so once their thread is running, they come out of the while True: loop, and the server gives them the new messages. In other words, I want to hold client's GET/receive open and not respond it as long as I want.
This process might take so long time. Maybe the chatroom is idle and there is no messages for a long time.
Right now the problem I have is that as soon as my client sends its first GET/receive message, it gets this error, even though I have set the timeout value in GET/receive request to be so much.
C:\Users\erfan\Desktop\web\client\venv\Scripts\python.exe C:\Users\erfan\Desktop\web\client\Client.py
Hossein
Welcome to chatroom Hossein ! Have a nice time !
Exception in thread Thread-1:
Traceback (most recent call last):
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\connectionpool.py", line 677, in urlopen
chunked=chunked,
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\connectionpool.py", line 426, in _make_request
six.raise_from(e, None)
File "<string>", line 3, in raise_from
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\connectionpool.py", line 421, in _make_request
httplib_response = conn.getresponse()
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 1321, in getresponse
response.begin()
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 296, in begin
version, status, reason = self._read_status()
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 265, in _read_status
raise RemoteDisconnected("Remote end closed connection without"
http.client.RemoteDisconnected: Remote end closed connection without response
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\requests\adapters.py", line 449, in send
timeout=timeout
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\connectionpool.py", line 727, in urlopen
method, url, error=e, _pool=self, _stacktrace=sys.exc_info()[2]
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\util\retry.py", line 410, in increment
raise six.reraise(type(error), error, _stacktrace)
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\packages\six.py", line 734, in reraise
raise value.with_traceback(tb)
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\connectionpool.py", line 677, in urlopen
chunked=chunked,
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\connectionpool.py", line 426, in _make_request
six.raise_from(e, None)
File "<string>", line 3, in raise_from
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\urllib3\connectionpool.py", line 421, in _make_request
httplib_response = conn.getresponse()
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 1321, in getresponse
response.begin()
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 296, in begin
version, status, reason = self._read_status()
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\http\client.py", line 265, in _read_status
raise RemoteDisconnected("Remote end closed connection without"
urllib3.exceptions.ProtocolError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\threading.py", line 917, in _bootstrap_inner
self.run()
File "C:\Users\erfan\AppData\Local\Programs\Python\Python37\lib\threading.py", line 865, in run
self._target(*self._args, **self._kwargs)
File "C:\Users\erfan\Desktop\web\client\Client.py", line 13, in coms
resp = requests.get("http://localhost:8081/receive", headers=headers,timeout=1000000)
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\requests\api.py", line 76, in get
return request('get', url, params=params, **kwargs)
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\requests\api.py", line 61, in request
return session.request(method=method, url=url, **kwargs)
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\requests\sessions.py", line 530, in request
resp = self.send(prep, **send_kwargs)
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\requests\sessions.py", line 643, in send
r = adapter.send(request, **kwargs)
File "C:\Users\erfan\Desktop\web\client\venv\lib\site-packages\requests\adapters.py", line 498, in send
raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', RemoteDisconnected('Remote end closed connection without response'))
===========================================================================
UPDATE:
The strange part is whenever I edit the GET/receive module to this:
def do_GET(self):
while True:
pass
everything works fine.
But when I do :
def do_GET(self):
t=threading.Thread(target=long_Poll,args=(self))
t.start()
def long_Poll(con):
client =None
while True:
pass
It gives the same error to the client!
I mean the problem is because I pass the self object to another function to respond? maybe it interrupts the connection? I remember having the same problem in Java socket programming where I would encounter to some bugs sometimes when I wanted to use a socket to communicate in two functions? However, here I only want to communicate in the long-polling function not anywhere else.
=======================================
update:
I also put my server and client code here. For brevity, I post the paste.ubuntu links here.
Client:
https://paste.ubuntu.com/p/qJmRjYy4Y9/
Server:
https://paste.ubuntu.com/p/rVyHPs4Rjz/
First time a client types, he enters his name and after that he starts sending GET/receive requests. Client can then send his messages to other people by sending POST/message requests. Any time a user send a message to the server, the server finds him (by his auth) and updates all other clients unseenMessages so that whenever their long-polling thread continued, they'll get the new messages and their clients also send another GET/receive message immediately.

I have found the answer. I was trying to have a multithreaded server using single thread syntax!
I followed this thread for having a multithreaded HTTP server
Multithreaded web server in python

Python socket ConnectionResetError: [Errno 54] Connection reset by peer vs socket.error: [Errno 104] Connection reset by peer

I'm having trouble debugging my code because I cannot understand the socket error being raised.
Here is the traceback.
Traceback (most recent call last):
File "clickpression.py", line 517, in <module> presser.main()
File "clickpression.py", line 391, in main
File "clickpression.py", line 121, in clickpress self.refresh_proxies(country=country)
File "clickpression.py", line 458, in refresh_proxies self.proxies = self.get_proxies(country=country)
File "helpers.py", line 72, in wrapper return func(*args, **kwargs)
File "clickpression.py", line 264, in get_proxies self.settings.SUPER_PROXY).read().decode('utf-8')
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/urllib/request.py", line 161, in urlopen return opener.open(url, data, timeout)
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/urllib/request.py", line 463, in open response = self._open(req, data)
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/urllib/request.py", line 481, in _open '_open', req)
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/urllib/request.py", line 441, in _call_chain result = func(*args)
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/urllib/request.py", line 1210, in http_open return self.do_open(http.client.HTTPConnection, req)
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/urllib/request.py", line 1185, in do_open r = h.getresponse()
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/http/client.py", line 1171, in getresponse response.begin()
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/http/client.py", line 351, in begin version, status, reason = self._read_status()
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/http/client.py", line 313, in _read_status line = str(self.fp.readline(_MAXLINE + 1), "iso-8859-1")
File "/usr/local/Cellar/python3/3.4.3/Frameworks/Python.framework/Versions/3.4/lib/python3.4/socket.py", line 374, in readinto return self._sock.recv_into(b)
ConnectionResetError: [Errno 54] Connection reset by peer
According to the errno library Errno 54 is errno.EXFULL which in the python 3 documentation is explained as exchange full.
To my understanding the Connection reset by peer is Errno 104 i.e errno.ECONNRESET.
So what does errno.EXFULL mean? and why does socket raise the error with a connection reset by peer description instead of exchange full. And or how are the two errors errno.EXFULL and errno.ECONNRESET related?
PS: I read that the errno 54 might be related to http proxy (I'm using a proxy in my code). If so, how?

According to the errno library Errno 54 is errno.EXFULL
Did you determine that by examining errno.errorcode[54]? Anyway - this errno library might be at fault. You could verify the meaning of an error code on your system by looking into errno.h, e. g. with the help of gcc:
gcc -xc -imacros errno.h -Wp,-P -E <(echo ECONNRESET)
Also, the Python documentation says:
To translate a numeric error code to an error message, use
os.strerror().
It may well be that error number 54 is ECONNRESET on your system, and that os.strerror(54) will attest that.
Now that you have verified that os.strerror(54) returns 'Exchange full', I am puzzled why the error number 54 and the error string Connection reset by peer do not match. If that happens on a system with strace or something similar, I would further check which error is returned by the operating system through use of strace -e network on the affected process.
Regarding your question about EXFULL: Its meaning seems somewhat system dependent; e. g. on Linux, EXFULL is returned from only a handful places in the kernel, the only network-related place being in br_if.c concerning network bridges, when no available bridge port number is found (other places are in USB and SCSI drivers).

I tried to use python to crew coin market on OKEX.com using WebSocket,cause the url is an outer address,i used a vpn service provided by us,but it still can work. here is the code an traceback.
from ws4py.client.threadedclient import WebSocketClient
class DummyClient(WebSocketClient):
def opened(self):
# self.send("{'event': 'addChannel', 'channel': 'ok_sub_futureusd_btc_ticker_this_week'}") #发送请求数据格式
# self.send("www.baidu.com")
self.send("{'event':'addChannel','channel':'ok_sub_spot_bch_btc_ticker'}")
def closed(self, code, reason=None):
print("Closed down", code, reason)
#服务器返回消息
def received_message(self, m):
print("recv:", m)
if __name__ == '__main__':
try:
# 服务器连接地址wss://real.okex.com:10440/websocket/okexapi
# ws = DummyClient('wss://real.okcoin.cn:10440/websocket/okcoinapi', protocols=['chat'])
ws = DummyClient('wss://real.okex.com:10440/websocket/okexapi', protocols=['chat'])
ws.connect()
#ws.send("my test...")
ws.run_forever()
except KeyboardInterrupt:
ws.close()

You can try this code to your project:
import ssl
ssl._create_default_https_context = ssl._create_unverified_context
if it not work,make sure the server open TLSv1 support.

Connection Reset by Peer with Python module urllib

What I'm tryng to do is to download images through Google Custom Search API using Python. It's my first time and maybe I'm making some banal error catching exceptions with Python.
It all works fine even when I get into some error which is not 10054 Connection Reset By Peer. The code is something like this, I've just taken out the useless part:
try:
urllib.request.urlretrieve(myUrl['link'],str(count)+'.jpg')
except URLError as e:
print(e.reason)
Sometimes it happens that connection is reset by peer and the console shows this error.
urllib.request.urlretrieve(myUrl['link'],str(count)+'.jpg')
File "C:\Python33\lib\urllib\request.py", line 210, in urlretrieve
block = fp.read(bs)
File "C:\Python33\lib\http\client.py", line 503, in read
return super(HTTPResponse, self).read(amt)
File "C:\Python33\lib\http\client.py", line 542, in readinto
n = self.fp.readinto(b)
File "C:\Python33\lib\socket.py", line 297, in readinto
return self._sock.recv_into(b)
ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host
Press any key to continue . . .
Now I'm not really interested in make that URL work, but I just want my loop to keep going and not to stop. How can I catch that exception?
Edit:
I also noticed that sometimes the code correctly catches the error and print(e.reason) correctly outputs [WinError 10054] without stopping the loop. That's very strange.

If you don't know the exact problem, you can catch all exceptions as so:
try:
urllib.request.urlretrieve(myUrl['link'],str(count)+'.jpg')
except URLError as e:
print(e.reason)
except KeyboardInterrupt as ki:
raise ki
except:
print("Unknown Error")

Best practice for handling exceptions from libraries imported by other libraries in Python?

What is the appropriate way for handling exceptions from libraries imported by other libraries in Python?
For example, I have a library called "pycontrol" that I import into my main program. "pycontrol" imports the "suds" library. The "suds" library, in turn, imports the "urllib2" library. I've noticed that when the "suds" library has trouble connecting to remote resources it is accessing through "urllib2," these exceptions trickle up to my main program.
My best guess at this point is to import urllib2 and suds into my global name space and catch typical exceptions that get thrown by them and aren't handled in "pycontrol".
Is there some other best practice as to how one might approach this?
A basic idea of what the snippet of code looks like (without importing suds or urllib2 into global name space):
import pycontrol.pycontrol as pc
print "Connecting to iControl API on LTM %s..." % ltm
try:
b = pc.BIGIP(hostname=ltm, username=user, password=pw,
wsdls=wsdl_list, fromurl=True,
debug=soap_debug)
except (<whattocatch>), detail:
print "Error: could not connect to iControl API on LTM %s... aborting!" % ltm
print "Details: %s" % detail
exitcode = 1
else:
print "Connection successfully established."
Here's a sample traceback:
Connecting to iControl API on LTM s0-bigip1-lb2.lab.zynga.com...
Traceback (most recent call last):
File "./register.py", line 507, in <module>
main()
File "./register.py", line 415, in main
b = build_bigip_object(ltm, user, pw, WSDLS, soap_debug = False)
File "./register.py", line 85, in build_bigip_object
debug=soap_debug)
File "build/bdist.macosx-10.6-universal/egg/pycontrol/pycontrol.py", line 81, in __init__
File "build/bdist.macosx-10.6-universal/egg/pycontrol/pycontrol.py", line 103, in _get_clients
File "build/bdist.macosx-10.6-universal/egg/pycontrol/pycontrol.py", line 149, in _get_suds_client
File "/Library/Python/2.6/site-packages/suds/client.py", line 111, in __init__
self.wsdl = reader.open(url)
File "/Library/Python/2.6/site-packages/suds/reader.py", line 136, in open
d = self.fn(url, self.options)
File "/Library/Python/2.6/site-packages/suds/wsdl.py", line 136, in __init__
d = reader.open(url)
File "/Library/Python/2.6/site-packages/suds/reader.py", line 73, in open
d = self.download(url)
File "/Library/Python/2.6/site-packages/suds/reader.py", line 88, in download
fp = self.options.transport.open(Request(url))
File "/Library/Python/2.6/site-packages/suds/transport/https.py", line 60, in open
return HttpTransport.open(self, request)
File "/Library/Python/2.6/site-packages/suds/transport/http.py", line 62, in open
return self.u2open(u2request)
File "/Library/Python/2.6/site-packages/suds/transport/http.py", line 118, in u2open
return url.open(u2request, timeout=tm)
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib2.py", line 383, in open
response = self._open(req, data)
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib2.py", line 401, in _open
'_open', req)
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib2.py", line 361, in _call_chain
result = func(*args)
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib2.py", line 1138, in https_open
return self.do_open(httplib.HTTPSConnection, req)
File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/urllib2.py", line 1105, in do_open
raise URLError(err)
urllib2.URLError: <urlopen error [Errno 8] nodename nor servname provided, or not known>

I think you answered you question yourself. Import urllib2 and catch the exception in your module.
from urllib2 import URLError
try:
# something
except URLError, e:
# Do something in case of error.

Why do you need to catch specific exceptions at all? After all, any exception (not only URLError) raised from b = pc.BIGIP(...) means you cannot go on.
I suggest:
import traceback
try:
b = pc.BIGIP(...)
except:
traceback.print_exc()
exitcode = 1
else:
do_something_with_connection(b)
Another idea: Why bother with catching the exception at all? The Python interpreter will dump a stack trace to stderr and exit the program when it encounters an unhandled exception:
b = bc.BIGIP(...)
do_something_with_connection(b)
Or if you need to write to an error log:
import logging
import sys
def main():
b = bc.BIGIP(...)
do_something_with_connection(b)
if __name__ == "__main__":
try:
main()
except:
logging.exception("An unexpected error occured")
sys.exit(1)