* origin/pr/172:
Say which repository caused the error in warnings
Only make qrexec calls when necessary
Squash more PyLint warnings
Decode stderr in repo qrexec calls
Fix error handling
Fix `self` being undefined when showing warnings
Only apply repo preferences when "OK" is clicked
Don't use asserts for error handling
Check that repo management succeeded
Remove unnecessary assert
Squash some PyLint warnings
Add UI for managing Qubes update repositories
Fix typo
FixesQubesOS/qubes-issues#4550
1edf363efe