arch-update: handle error exit of checkupdates

[uykusuz]

checkupdates v1.2.0 exits with exit code 1 when there are no updates.

Expected behavior

arch-update should return that the system is up-to-date when checkupdates exits with an error.

Actual behavior

arch-update fails and the whole blocklet won't get displayed.

i3blocks config relevant to blocklet(s)

arch-update

Output of blocklet(s) when run from command line

Traceback (most recent call last):
  File "./arch-update", line 109, in <module>
    updates = get_updates()
  File "./arch-update", line 65, in get_updates
    output = check_output(['checkupdates']).decode('utf-8')
  File "/usr/lib/python3.7/subprocess.py", line 395, in check_output
    **kwargs).stdout
  File "/usr/lib/python3.7/subprocess.py", line 487, in run
    output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['checkupdates']' returned non-zero exit status 1.

Output of any relevant other commands that might help diagnostics

checkupdates exits with 1 when there are no updates.

[Johannes Lange]

Thanks, it's fixed in f2715bc now.