Due to test modules being copied in subdirectories of the
build directory by setuptools, it makes pytest fail by raising
ImportPathMismatchError exceptions when invoked from root
directory of the module.

So ignore the build folder to discover tests.

The addition of '-p no:pytest_swh_core' in pytest.ini is needed to
prevent pytest from loading the pytest_swh_core plugin which we do not
need here and which would require some more dependencies (e.g.
requests).

pytest wastes a lot of time in .hypothesis and .git; this commit excludes them.

to prevent warnings