migrate CI to github actions and run python unittests with python2 and python3.
Remove coveralls instrumentation from CI
ENDRELEASENOTES
[x] coverall needs token to be moved from travis to here
I removed the coverall instrumentation because it is not possible to share secrets with workflows that are run on forked repositories but that would be necessary for successfully running coveralls.
BEGINRELEASENOTES
ENDRELEASENOTES
I removed the coverall instrumentation because it is not possible to share secrets with workflows that are run on forked repositories but that would be necessary for successfully running coveralls.