Pickle5 backport support for Python3.5

[suquark]

No description provided.

[suquark]

The tests have all passed, except 2 issues:

• We got ValueError: must use protocol 4 or greater to copy this object; since __getnewargs_ex__ returned keyword arguments., which seems to be a 'correct' behavior under python3.5
• Numpy refused to support python3.5, but it can be simply changed by modifying the line checking the python version.

[robertnishihara]

Would it make sense to add 3.5 to Travis?

[pcmoritz]

@suquark Can you fix the travis tests and add tests for python 3.5 so we can get this merged?

[suquark]

The Arm64 errors seem not related.

[pcmoritz]

@pitrou Can you take a look at this and see if we can get the PR merged? It would be great to do that and prepare a new release of pickle5-backport! Let me know if we can help with anything on this front!

@suquark Says the error on ARM is unrelated to this PR and already happens on the current master of this repo (due to a new numpy release that breaks it).

[pitrou]

Could you split Python 3.5 support into a separate PR?

[suquark]

@pitrou Sure. Let me make one that only contains the Python3.5 support. BTW, will you also add the bpo-39492 fix (or just sync up with the latest cpython pickle)? This is also critical I think. Otherwise I would also create another PR to fix the reference count issue.

[pitrou]

I think syncing would be best, is that something you want to try to do?

[suquark]

Yes, so I will create two PRs, one for the syncing, one for the python3.5 support (based on the synced version)

[suquark]

This PR has been divided into #15 and #16.