Update tox to 2.9.0

[pyup-bot]

There's a new version of tox available.
You are currently using 2.7.0. I have updated it to 2.9.0

These links might come in handy: PyPI | Changelog | Docs

Changelog

2.9.0

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

Features

• tox --version now shows information about all registered plugins - by
  :user:obestwalter (544 <https://github.com/tox-dev/tox/issues/544>_).

Bugfixes

• skip_install overrides usedevelop (usedevelop is an option to
  choose the installation type if the package is installed and skip_install
  determines if it should be installed at all) - by :user:ferdonline (571 <https://github.com/tox-dev/tox/issues/571>_).

Misc

• :pull:635 inherit from correct exception - by :user:obestwalter
  (635 <https://github.com/tox-dev/tox/issues/635>_).
• spelling and escape sequence fixes - by :user:scoop
  (637 <https://github.com/tox-dev/tox/issues/637>_ and
  638 <https://github.com/tox-dev/tox/issues/638>_).
• add a badge to show build status of documentation on readthedocs.io -
  by :user:obestwalter.

Improved Documentation

• add towncrier <https://github.com/hawkowl/towncrier>_ to allow adding
  changelog entries with the pull requests without generating merge conflicts;
  with this release notes are now grouped into four distinct collections:
  Features, Bugfixes, Improved Documentation and Deprecations and Removals. (614 <https://github.com/tox-dev/tox/issues/614>_)

2.8.2

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

• 466 <https://github.com/tox-dev/tox/issues/466>_: stop env var leakage if popen failed with resultjson or redirect

2.8.1

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

• :pull:599: fix problems with implementation of :issue:515.
  Substitutions from other sections were not made anymore if they were not in envlist.
  Thanks to Clark Boylan (:user:cboylan) for helping to get this fixed (:pull:597).

2.8.0

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

• :issue:276: Remove easy_install from docs (TL;DR: use pip). Thanks Martin Andrysík (:user:sifuraz).

• :issue:301: Expand nested substitutions in tox.ini. Thanks :user:vlaci. Thanks to Eli Collins
  (:user:eli-collins) for creating a reproducer.

• :issue:315: add --help and --version to helptox-quickstart. Thanks :user:vlaci.

• :issue:326: Fix OSError 'Not a directory' when creating env on Jython 2.7.0. Thanks Nick Douma (:user:LordGaav).

• :issue:429: Forward MSYSTEM by default on Windows. Thanks Marius Gedminas (:user:mgedmin) for reporting this.

• :issue:449: add multi platform example to the docs. Thanks Aleks Bunin (:user:sashkab) and :user:rndr.

• :issue:474: Start using setuptools_scm for tag based versioning.

• :issue:484: Renamed py.test to pytest throughout the project. Thanks Slam (:user:3lnc).

• :issue:504: With -a: do not show additional environments header if there are none. Thanks :user:rndr.

• :issue:515: Don't require environment variables in test environments where they are not used.
  Thanks André Caron (:user:AndreLouisCaron).
• :issue:517: Forward NUMBER_OF_PROCESSORS by default on Windows to fix multiprocessor.cpu_count().
  Thanks André Caron (:user:AndreLouisCaron).

• :issue:518: Forward USERPROFILE by default on Windows. Thanks André Caron (:user:AndreLouisCaron).

• :pull:528: Fix some of the warnings displayed by pytest 3.1.0. Thanks Bruno Oliveira (:user:nicoddemus).

• :pull:547: Add regression test for :issue:137. Thanks Martin Andrysík (:user:sifuraz).

• :pull:553: Add an XFAIL test to reproduce upstream bug :issue:203. Thanks
  Bartolomé Sánchez Salado (:user:bartsanchez).

• :pull:556: Report more meaningful errors on why virtualenv creation failed. Thanks :user:vlaci.
  Also thanks to Igor Sadchenko (:user:igor-sadchenko) for pointing out a problem with that PR
  before it hit the masses ☺

• :pull:575: Add announcement doc to end all announcement docs
  (using only CHANGELOG and Github issues since 2.5 already).

• :pull:580: Do not ignore Sphinx warnings anymore. Thanks Bernát Gábor (:user:gaborbernat).

• :pull:585: Expand documentation to explain pass through of flags from deps to pip
  (e.g. -rrequirements.txt, -cconstraints.txt). Thanks Alexander Loechel (:user:loechel).

• :pull:588: Run pytest wit xfail_strict and adapt affected tests.

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

Happy merging! 🤖

[pyup-bot]

Closing this in favor of #29