Ignore .pytest_cache

[hugovk]

Pytest now uses a .pytest_cache directory. Ignore it.

The default cache directory has been renamed from .cache to .pytest_cache after community feedback that the name .cache did not make it clear that it was used by pytest. (#3138)

https://docs.pytest.org/en/latest/changelog.html#pytest-3-4-0-2018-01-30

[berkerpeksag]

Thanks for the PR, but we usually prefer keeping things like this in a user's own global .gitignore file. We have cleaned up our .gitignore file to encourage people to use a global one in commit 4185b2b.

[tilgovi]

In this case, pytest is in use by the project and it's not user specific. I'd be fine with this.

[berkerpeksag]

@tilgovi fine by me, I don't have a strong objection. I already added it to my own global .gitignore file since I use pytest in multiple projects.

[tilgovi]

Merged it :). Thanks.