Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

$ git checkout v2.2.x$ git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

$ git cherry-pick -m1 d162b6d2b8d001f893bc7a0a073f77f3ff445847

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

$ git commit -am "Backport PR #16311: don't override non-Python signal handlers"

4. Push to a named branch :

git push YOURFORK v2.2.x:auto-backport-of-pr-16311-on-v2.2.x

5. Create a PR against branch v2.2.x, I would have named this PR:

"Backport PR#16311 on branch v2.2.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free tosuggest an improvement.

The 2.2.x branch does not have the restoring logic, rather than implicitly backport that as well, only push this back to 3.1.x

Thanks@stevengj ! Congratulations on your first merged Matplotlib pull request 🎉 Hopefully we will hear from you again.

Hi, I had a similar issue that only appeared when I ran Matplolib fromParaview's pvpython - is this fix something that I can implement or do I have to wait for the next release on conda? Thanks and regards. Tim

Edit: I just applied the 2-line fix detailed in the link at the top of the page manually in my conda-managed file:
~/anaconda3/envs/sound6/lib/python3.7/site-packages/matplotlib/backends/backend_qt5.py

I'm not sure if this is the best idea or not, but it fixes the issue for the moment!

Sorry, just to add an additional comment (I know you've already sent off the patch) - would it be a little more robust to checkif old_signal is not None? I realise that in this case, the non-None returns ofsignal.getsignal(SIGINT) (signal.SIG_IGN andsignal.SIG_DFL) both currently evaluate to Python 'truthy', so that justif old_signal works at the moment, but would this in some foreseeable circumstance change? Not a criticism but a question, as I'm not well versed in these libraries! Thanks for the fixes!

From my understanding of the Python docs, any valid signal handler will have a True truth value.is not None would be fine too, of course.