Dependency issues

I noticed that both pandas and numpy are breaking the test suite currently.

There's a known issue with numpy>=1.20 and lalsuite (although it is fixed on master, lalsuite!1526 (merged)).

It looks like deepdish is finally officially dead as of pandas==1.2.1 (at least). For now we can pin the pandas version until we are able to remove the deepdish dependency. See !889 (closed).