Python Paths

[sjunges]

Our functions that take paths as input currently expect strings. Should we instead allow (or even enforce) pathlib.Path?

[volkm]

I would be in favor of using pathlib.Path.
My approach would be twofold: we first use pathlib.Path but allow strings as a fall-back (and give a deprecation warning). Later, we can remove string support altogether. Or should we simply migrate at once?