Import urllib3 exception classes explicitly

[tiewei]

urllib3.exceptions module will be renamed as requests.packages.urllib3.exceptions when python-requests is loaded, when tries to catch urllib3.exceptions, it actually tries to catch requests.packages.urllib3.exceptions, at the same time urllib3 will always tries to throw exceptions with its own module name. As a result, no exceptions from urllib3 will be treated correctly (e.g. failed on reconnect). This commit imports urllib3 exception classes explicitly, so when tries to compare exception, it will always compares with the one from the same module.

[tiewei]

some e.g. proves the problem

-bash-4.2# python
Python 2.7.5 (default, Aug 29 2016, 10:12:21)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import urllib3
>>> import requests
>>> urllib3.exceptions.HTTPError.__module__
'requests.packages.urllib3.exceptions'
>>> from urllib3.exceptions import HTTPError
>>> HTTPError.__module__
'urllib3.exceptions'
>>> urllib3.__version__
'1.10.2'
>>> requests.__version__
'2.6.0'

[coveralls]

Coverage increased (+0.02%) to 88.462% when pulling 3eb214603b858b215a0498bdc96d3c7db27b832a on TieWei:urllib3_import into 0d0145f5e835aa032c97a0a5e09c4c68b7a03f66 on jplana:master.

[ashcrow]

:+1: Looks good to me.

[juledwar]

+1

[vhosakot]

👍 great catch!