Update setup.py and test flow

[ob-stripe]

r? @brandur-stripe
cc @stripe/api-libraries

(This is for the upcoming v2.0.)

Update setup.py and test flow:

• refactor setup.py to use best practices described in https://github.com/pypa/sampleproject/blob/master/setup.py

• bump minimum requests version to 2 (current major version)

• add requests[security] to dependencies for Python 2. This should help with TLS 1.2 issues, e.g. when using the default OS X Python interpreter.

• removed pytest-runner from setup_requires to avoid installing the package for every setup.py invocation. Instead use a custom PyTest command as described here.

• use pytest-xdist to distribute tests over multiple cores. This is not very useful when running tests on a reasonably powerful local machine, but gives a noticeable speed increase on Travis.

• use find_packages to discover packages automatically

• Greatly simply tox.ini by putting coverage and flake8 configurations in dedicateds files, and simply running python setup.py test

• Don't install pycurl package when running tests as it wasn't actually used anywhere

• Remove allow_failures from Travis configuration as we probably want to not merge PRs that break PyPy or 3.7 compatibility

[brandur-stripe]

Nice cleanups!

Just to confirm, all test invocations are still the same right? i.e., no changes are required in README.md or anything?

LGTM.

[ob-stripe]

Just to confirm, all test invocations are still the same right? i.e., no changes are required in README.md or anything?

Oh, good point, my update to tox.ini broke the possibility of passing custom parameters. This is now fixed: if you don't pass any parameters, then it will run with -n auto (which spreads tests over as many workers as there are CPU cores), otherwise it will use your parameters. The examples from the README will still work.