Catch thrown OSError by python 3.7 when creating a connection

[danjo133]

This is needed to use kafka-python with python 3.7.

It builds on #1669 and the solution is a slightly modified version of a comment on #1661

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This change is 

[danjo133]

Should I update tox.ini, setup.py, .travis.yml as well to add Python 3.7 support/testing?

[dpkp]

python bug report here: https://bugs.python.org/issue31122

It seems like wrap_socket() could also raise OSError?

[danjo133]

So, that gets raised when a socket disconnects? I would say that is another error. This PR is for OSError that is raised when trying to connect normally. I can add a catch for 31122 as well if you want though. How do you want it handled in that case? should it raise SSLEOFError or set errno to something like ENOTCONN ? If I understand the bug report, then if you get hit by that, then your connection has been closed and you need to try to reconnect in some way, which I guess should be up to the user.

[danjo133]

@dpkp Do you want me to do anything more/different with this PR?

[dpkp]

We've finally got python 3.7 automated testing working on travis, so I think we're good to go. Would love more test coverage wrt SSL connections though.