Fix issue with python coverage tests
Fix issue with python coverage tests

The recently introduced check for python libraries required only for testing
(commit 27df5b736ef72b3b12c07f32d64dbac95fe7a5ba) was not correct. This
patch fixes the issue.

Signed-off-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>
Reviewed-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>

dimara/ganeti,ganeti/ganeti,andir/ganeti,leshchevds/ganeti,andir/ganeti,apyrgio/ganeti,yiannist/ganeti,apyrgio/snf-ganeti,ganeti-github-testing/ganeti-test-1,onponomarev/ganeti,grnet/snf-ganeti,andir/ganeti,bitemyapp/ganeti,leshchevds/ganeti,yiannist/ganeti,yiannist/ganeti,bitemyapp/ganeti,grnet/snf-ganeti,apyrgio/ganeti,leshchevds/ganeti,dimara/ganeti,mbakke/ganeti,ganeti/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,ganeti/ganeti,onponomarev/ganeti,ganeti-github-testing/ganeti-test-1,mbakke/ganeti