Update pytest to 3.1.2

[pyup-bot]

There's a new version of pytest available.
You are currently using 3.1.0. I have updated it to 3.1.2

These links might come in handy: PyPI | Changelog | Repo | Homepage

Changelog

3.1.2

=========================

Bug Fixes

• Required options added via pytest_addoption will no longer prevent using
  --help without passing them. (1999)

• Respect python_files in assertion rewriting. (2121)

• Fix recursion error detection when frames in the traceback contain objects
  that can't be compared (like numpy arrays). (2459)

• UnicodeWarning is issued from the internal pytest warnings plugin only
  when the message contains non-ascii unicode (Python 2 only). (2463)

• Added a workaround for Python 3.6 WindowsConsoleIO breaking due to Pytests's
  FDCapture. Other code using console handles might still be affected by the
  very same issue and might require further workarounds/fixes, i.e. colorama.
  (2467)

Improved Documentation

• Fix internal API links to pluggy objects. (2331)

• Make it clear that pytest.xfail stops test execution at the calling point
  and improve overall flow of the skipping docs. (810)

3.1.1

=========================

Bug Fixes

• pytest warning capture no longer overrides existing warning filters. The
  previous behaviour would override all filters and caused regressions in test
  suites which configure warning filters to match their needs. Note that as a
  side-effect of this is that DeprecationWarning and
  PendingDeprecationWarning are no longer shown by default. (2430)

• Fix issue with non-ascii contents in doctest text files. (2434)

• Fix encoding errors for unicode warnings in Python 2. (2436)

• pytest.deprecated_call now captures PendingDeprecationWarning in
  context manager form. (2441)

Improved Documentation

• Addition of towncrier for changelog management. (2390)

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖