Update cssutils to 2.15.0

[pyup-bot]

This PR updates cssutils from 2.3.1 to 2.15.0.

Changelog

2.15.0

=======

Features
--------

- Added support for Selectors Level 4 pseudo-classes that accept full selector lists as arguments (:has(), :is(), :where(), :matches(), :any()). (66)
- Fixed pseudo-class specificity calculation. Pseudo-classes (e.g. ``:hover``, ``:last-child``, ``:nth-child()``) now correctly contribute to the class-weight column per the CSS Selectors spec. (76)

2.14.0

=======

Features
--------

- Moved tests out of the install. (74)

2.13.0

=======

Features
--------

- Replaced encutils with separate package of the same name. (73)

2.12.0

=======

Features
--------

- Simplify dictionary keys access in _ColorProd function. (63)
- Allow font-face rules nested inside media rules. (68)
- Added REM and other CSS3 length units to length macros. (69)

2.11.1

=======

Bugfixes
--------

- Consolidated license to simply LGPL 3. (52)

2.11.0

=======

Features
--------

- Reduced cyclomatic complexity in selector module. (47)

2.10.3

=======

Bugfixes
--------

- Fixed DeprecationWarning with cgi module.

2.10.2

=======

Bugfixes
--------

- Remove optional dependency only required on unsupported Python versions. (48)

2.10.1

=======

Bugfixes
--------

- Replace xunit-style setup with pytest fixtures. (45)

2.10.0

=======

Features
--------

- getPropertyValue now allows specifying a default value. (42)

2.9.0

======

Features
--------

- Made URL fetcher lenient to missing metadata.

2.8.0

======

Features
--------

- Require Python 3.8 or later.


Bugfixes
--------

- Made some unreachable tests reachable.

2.7.1

======

36: Refactored to restore docs builds without warning-errors.

2.7.0

======

35: Updated deprecated usage of ``cgi`` module.

34: Updated deprecated setup/teardown from ``nose`` in tests.

Other miscellaneous cleanup and packaging updates.

2.6.0

======

14: Added support for custom CSS variables with ``--`` prefix.

2.5.1

======

Some refactoring.

2.5.0

======

Substantial code refresh. Ported tests to native pytest.

Enrolled project with Tidelift.

2.4.2

======

24: Added Python 3.11 compatibility to tests.

2.4.1

======

22: Removed ``cssutils.tests.basetest.get_resource_filename``.
21: Cleaned up docs so they build without warnings.

2.4.0

======

Require Python 3.7.

Links

• PyPI: https://pypi.org/project/cssutils
• Changelog: https://data.safetycli.com/changelogs/cssutils/
• Docs: https://pythonhosted.org/cssutils/

[pyup-bot]

Closing this in favor of #1087