Ignore set_session in the coverage
This method is marked as a @app.before_request which is known in flask
to not be triggered:
http://flask.pocoo.org/docs/1.0/testing/#other-testing-tricks
We looked for ways to test it and it turned out to be more a time-sync
than something beneficial. So removing this function from the coverage
for now.
Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>