pypi packages broken: 0.5.0a1; 0.5.0a2

[lukasmittag]

the pypi packages 0.5.0a1 and 0.5.0a2 are broken because they're a work in progress. 0.5.0 is still operational.

[erikbosch]

We could consider yanking them, see https://docs.pypi.org/project-management/yanking/