Log Message:
py-test-cov: updated to 2.9.0

2.9.0:
* Fixed ``RemovedInPytest4Warning`` when using Pytest 3.10.
* Made pytest startup faster when plugin not active by lazy-importing.
* Various CI improvements.
* Various Python support updates (drop EOL 3.4, test against 3.8 final).
* Changed ``--cov-append`` to always enable ``data_suffix`` (a coverage setting).
  Contributed by Harm Geerts in
* Changed ``--cov-append`` to handle loading previous data better
  (fixes various path aliasing issues).
* Various other testing improvements, github issue templates, example updates.
* Fixed internal failures that are caused by tests that change the current \ 
working directory by
  ensuring a consistent working directory when coverage is called.