It seems like some install fail if we do not upgrade at the same time.
fixes the error:
<https://gist.github.com/MartinPulec/602c195ec03933f826668b3ec1239d02>
+ use more descriptive name for the CI step
+ drop final \ in the Dockerfile (as mentioned in the CI output linked above)
run the same test cases for both Arch Linux and Ubuntu
+ rename Dockerfile.arch to Dockerfile.archlinux (the former is a bit
misleading - arch==architecture or what?)
