Make sure stdout and stderr ends up in logs

[ErikBjare]

Needed when debugging certain issues like #229, it's been a recurring issue.

Things we'd also want:

• Traceback to end up in logs
• Weird output from subprocesses (such as osascript in aw-watcher-window on macOS)

See this for a possible solution: https://stackoverflow.com/a/39215961/965332

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ErikBjare]

I don't care enough about this to keep it open. Closing.