Log Message:
py-fixtures: updated to 4.1.0

4.1.0

* Drop support for Python 3.6 (EOL)
* Add a new ``WarningsFilter`` filter, allowing users to filter warnings as
  part of their tests, before restoring said filters.

4.0.1

* Remove ``testtools`` from ``requirements.txt`` as well.

4.0.0

* Add missing APIs to ``FakeProcess``, making it match ``Popen``.
* Dropped support for Python 2.7, Python 3.4 and Python 3.5 (EOL).
* Added support for Python 3.6-3.10.
* Add possibility to reset the ``FakeLogger``.
* Access ``mock.DEFAULT`` lazily rather than at import time so ``mock`` can
  be overridden with something else.
* Support all ``subprocess.Popen`` arguments up to Python 3.10.
* Move ``testtools`` requirement to a new ``fixtures[streams]`` extra.