fix: ctrl-c now runs shutdown routines

[Hanicef]

I added SIGINT to the signal handler in __init__.py, which is the signal generated by Ctrl-C.
This fixes #1370 .

[dgw]

Thanks for this, works for me on Linux. I'm sure macOS will work fine, too, because it's a Unix-like—but I'll see if I can find an opportunity to test on Windows too for good measure.

I remember toying with this exact approach, and thought I had committed it in a branch somewhere… Can't find mine, maybe I tossed it to work on something else.

[Hanicef]

No problem. I really wanted to just fix this bug as it was bugging me (no pun intended) that the shutdown routines didn't run.

[dgw]

Turns out Ctrl-C doesn't seem to work on Windows at all. Pressing it throws an AttributeError because signal.SIGUSR1 is missing. Tested on Win7, the newest Windows version I have. Test results from anyone running Windows 8 or 10 would be welcome, I guess, but git blame tells me Ctrl-C has been broken on Windows for at least five years (the length of time since the erroring code was last changed).

Basically, I won't lose any sleep over merging this with a pre-existing bug included. 😹 I'll leave it open a bit in case anyone else comes along with test results from newer Windows (or I find an opportunity to test one/both myself), but no matter what this PR is getting approved.