Code review comment for ~andersson123/autopkgtest-cloud:trusty_xenial_amd_64

I looked at the example run in staging and it looks great, thanks!

I missed this earlier but the check that you are adding is outside of the 'try:' 'finally:' block and the 'finally:' block calls shutil.rmtree(work_dir). Was that change deliberate? If not I think it'd be best if the release and arch check were inside the 'try:' section.