Python isn't always installed in /usr/bin. If we hard-code the path,
these tests will fail on *BSD because they install python in different
prefixes such as /usr/local and /usr/pkg.
This adds tests for the network panel based on the test service found in
NetworkManager. Another possible solution may be to use the one from
dbusmock, however NetworkManager already has readily available code to
write tests in C which makes checking the widget hierarchy easier.