gitlab-ci: new test case of pip installs on Ubuntu/trusty
gitlab-ci: new test case of pip installs on Ubuntu/trusty

Ubuntu/trusty is used as the base image for CI systems like Travis, as well
as Microsoft Subsystem for Linux.  SO we need to provide working options.

fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroidserver,f-droid/fdroidserver