Make gen_addons_table test generate coverage
Make gen_addons_table test generate coverage

This is done by invoking subprocess with sys.executable,
pytest-cov does the rest.

Also change test style to pytest instead of unittest.

OCA/maintainer-tools,OCA/maintainer-tools,acsone/maintainers-tools,Yajo/maintainer-tools,Yajo/maintainer-tools,OCA/maintainer-tools,acsone/maintainer-tools,acsone/maintainer-tools,Yajo/maintainer-tools,acsone/maintainers-tools,Yajo/maintainer-tools,OCA/maintainer-tools,acsone/maintainers-tools,acsone/maintainer-tools,acsone/maintainer-tools