Fix ament_get_pytest_cov_version for newer versions of pytest

[christophebedard]

Newer versions of pytest do not display plugin versions by default. They require providing the --version option twice. See pytest-dev/pytest#7169.

$ python3 -m pytest --version
pytest 6.2.1
$ python3 -m pytest --version --version
This is pytest version 6.2.1, imported from /home/chris/.local/lib/python3.8/site-packages/pytest/__init__.py
setuptools registered plugins:
  pytest-cov-2.10.1 at /home/chris/.local/lib/python3.8/site-packages/pytest_cov/plugin.py
  pytest-repeat-0.9.1 at /home/chris/.local/lib/python3.8/site-packages/pytest_repeat.py
  pytest-rerunfailures-9.1.1 at /home/chris/.local/lib/python3.8/site-packages/pytest_rerunfailures.py
  colcon-core-0.6.1 at /home/chris/.local/lib/python3.8/site-packages/colcon_core/pytest/hooks.py
  pytest-mock-1.10.4 at /usr/lib/python3/dist-packages/pytest_mock.py

It also works fine on older versions (using sudo here to use the version installed from apt).

$ sudo python3 -m pytest --version
This is pytest version 4.6.9, imported from /usr/lib/python3/dist-packages/pytest.py
setuptools registered plugins:
  pytest-cov-2.8.1 at /usr/lib/python3/dist-packages/pytest_cov/plugin.py
  colcon-core-0.6.1 at /usr/lib/python3/dist-packages/colcon_core/pytest/hooks.py
  pytest-mock-1.10.4 at /usr/lib/python3/dist-packages/pytest_mock.py
$ sudo python3 -m pytest --version --version
This is pytest version 4.6.9, imported from /usr/lib/python3/dist-packages/pytest.py
setuptools registered plugins:
  pytest-cov-2.8.1 at /usr/lib/python3/dist-packages/pytest_cov/plugin.py
  colcon-core-0.6.1 at /usr/lib/python3/dist-packages/colcon_core/pytest/hooks.py
  pytest-mock-1.10.4 at /usr/lib/python3/dist-packages/pytest_mock.py

Finally, fix version regex for pytest-cov.

[hidmic]

LGTM pending green CI up to tracetools_test:

• Linux
• Linux-aarch64
• macOS
• Windows