Code review comment for ppa-dev-tools:error-handling-cleanup

Thanks Athos, that's a good idea. I've added it defined as EX_KEYBOARD_INTERRUPT. In fact while adding it I spotted a couple other places for it.

$ git merge --ff-only error-handling-cleanup
Updating 1a457e7..03b736c
Fast-forward
 ppa/ppa.py | 20 ++++++++++----------
 scripts/ppa | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++--------------------------
 2 files changed, 65 insertions(+), 36 deletions(-)
$ git push
Total 0 (delta 0), reused 0 (delta 0), pack-reused 0
To git+ssh://git.launchpad.net/ppa-dev-tools
   1a457e7..03b736c main -> main