Log Message:
py-test-cov: updated to 2.12.0

2.12.0 (2021-05-14)
* Added coverage's `toml` extra to install requirements in setup.py.
* Fixed ``pytest_cov.__version__`` to have the right value (string with version \ 
instead of a string
  including ``__version__ =``).
* Fixed license classifier in ``setup.py``.
* Fixed *commits since* badge.