Tests not exiting properly

[ageorgou]

In the last few days, we have noticed that pytest does not exit even after finishing all the tests and printing the report. This also means that sometimes Travis fails due to timing out, even if all the tests pass. The same also happens on local development setups, so it doesn't look like a Travis problem.

This doesn't happen consistently, but it seems to have become more frequent in the last week, so it might be related to recent changes, somewhere between da1f29b and f299dd2. Changing the NammuController to a pytest-style fixture (afe0835) didn't seem to make much difference.

It may be that Nammu spawns some other process or component that is not always properly deleted, hence letting pytest wait. This link could have some solutions for ensuring that all Swing components are destroyed.