Make plugins/mathematica/bin/realpath.py python 3

[opoplawski]

No description provided.

[da-liii]

@jgmbenoit we expected small and testable pull request, #79 is too big

And this pull request seems to be the missing part of your big pull request

[opoplawski]

I'm not sure why you are addressing jgmbenoit here. I also don't see why #79 is too big.

[da-liii]

I also don't see why #79 is too big.

Theoretically, we should test all changes before it is get merged.

It ( #79 ) is too big to be tested carefully.