Catch and report all errors raised when invoking command hooks

[ArneBab]

This should fix https://github.com/ch11ng/exwm/issues/842 (according to the discussion in the issue). I just nabbed this commit from https://github.com/daviwil/exwm/commit/7b1be884124711af0a02eac740bdb69446bc54cc

[medranocalvo]

@ArneBab, Thank you for bringing this up. I believe that need permission from @daviwil is needed, or at least warranted. @daviwil, would you like this change to be merged into EXWM?

[daviwil]

Yes! However, is it small enough to not require FSF copyright assignment? I still haven't arranged that yet.

[medranocalvo]

@daviwil, great! Yes, it's not needed for small changes, but will be needed in the future. I'd like more contributions from you!

For perspective, starting the assignment process involves sending an e-mail:

To: assign@gnu.org

REQUEST: SEND FORM FOR PAST AND FUTURE CHANGES

[What is the name of the program or package you're contributing to?]
GNU Emacs and GNU ELPA.
[Did you copy any files or text written by someone else in these changes? Even if that material is free software, we need to know about it.]

[Do you have an employer who might have a basis to claim to own your changes? Do you attend a school which might make such a claim?]

[For the copyright registration, what country are you a citizen of?]

[What year were you born?]

[Please write your email address here.]

[Please write your postal address here.]

[Which files have you changed so far, and which new files have you written so far?]

Then it gets more painstaking: signatures are needed. (Accommodations can be made if necessary, AFAIU.)

More details at https://www.gnu.org/software/emacs/manual/html_node/emacs/Copyright-Assignment.html

---

I'll complete the submission and merge as time permits. (Might take some time.) Thank you both @ArneBab and @daviwil.

[daviwil]

Yep, I've already got the process started with the FSF for both Emacs and Guile but I still need to bug a VP at my employer to approve it :/ Probably won't happen very soon! Hopefully this change is mergeable without it.

[medranocalvo]

Force-pushed with the following changes:

• simplify code using xcb-debug:backtrace
• run post-command-hook even if pre-command-hook fails. (Is this incorrect?)
• adjusted commit message Please test again with a failing hook.

[ArneBab]

I merged your changes. @daviwil can you test whether it still works for you?

[medranocalvo]

I merged this change into master (post 0.28).

Thank you @daviwil for the fix and thank you @ArneBab for making it happen.