Add Python 3.7 compatibility

[benmwebb]

Compilation of Python wrappers fails with Python 3.7 because
the Python folks changed their C API such that
PyUnicode_AsUTF8AndSize() now returns a const char* rather
than a char*. Add a patch to work around. Relates #4086.

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[benmwebb]

I signed it!

[anandolee]

Thanks for your PR

Is it the only thing that we need to fix for python3.7? Can you also help add python3.7 in tests.sh as well:
https://github.com/google/protobuf/blob/00d32539c6aa0c4efe9577561a00f443edd9a417/tests.sh

[benmwebb]

Is it the only thing that we need to fix for python3.7?

To the best of my knowledge, yes.

Can you also help add python3.7 in tests.sh as well

I don't know enough about your build system to confidently do that, but it looks like you run this on Travis, and I do know that making Python 3.7 work on Travis is a little involved because they require a newer OpenSSL than is present in Ubuntu Trusty - see travis-ci/travis-ci#9069.

[anandolee]

Thanks, we can add the 3.7 tests in other RPs.

[anandolee]

CLA is still complain. Can you double check?

[benmwebb]

CLA is still complain. Can you double check?

Just checked at https://cla.developers.google.com/clas and it shows I have a Google Individual CLA signed Jul 03, 2018 09:57 PDT.

[anandolee]

Are you using a different email address on your commit? It shows you are using ben@salilab.org for the commit, are you using this email to sign CLA and this email is set on your github account?

[benmwebb]

Right, ben@salilab.org is the commit email and is tied to my GitHub account. It is also an alternate email for my Google account, so all should be good there too. I just updated the CLA to add my GitHub username - maybe that will fix things at your end.

[googlebot]

CLAs look good, thanks!

[handlerbot]

Hi protobufferians --

TY @benmwebb for getting this fix in! 🌟

Is there anywhere I see the roughly planned schedule for the next release (3.7.0 or 3.6.2?), so we can figure out if we should wait for it, or patch this into protobuf 3.6.1 after we download it, if we are trying to build against Python 3.7.

Thanks!

[acozzette]

@handlerbot We don't have a set timeline for when our next release will be, but we will most likely do a 3.7.0 release before the end of the year (we probably won't be doing any more 3.6 patch releases).

[kkdd]

I look forward to python-3.7-compatible protobuf 3.6.x release, beause protobuf 3.6.1.1 or earlier is incompatible with it.