Python runner doesn't exit when gauge gets SIGINT

[bherw]

Describe the bug
When gauge gets terminated, gauge python keeps running, though it doesn't keep executing specs

To Reproduce
Steps (or project) to reproduce the behavior:

1. Initialise a gauge project with some specs
2. Run gauge in a terminal
3. Press Ctrl+C to send SIGINT to gauge
4. Gauge exits, but check ps -fC python3 to see start.py and start.sh are still running.

Expected behavior
The python runner should exit cleanly. I should not have 20 start.py python3 processes running on my system after doing a few test runs.

In addition, I have some AbstractContentManager resources which need to get cleaned up after the test harness exits, whether it exits with an error or otherwise. Right now these are getting cleaned up in the @after_suite hook, so it would be nice if that could still get called on an abnormal exit. Alternatively, perhaps the test harness can help with managing and cleaning up AbstractContentManagers.

Versions:

• Ubuntu 20.04
• Python version 3.8

Gauge version: 1.4.1
Commit Hash: a82478a

Plugins
-------
html-report (4.1.0)
python (0.3.17)
screenshot (0.1.0)