BUG: is comparison (almost) always False for pandas.Index

[veni-vidi-vici-dormivi]

Comparing two pandas.Index with is will almost always return False since pandas.Index are always different objects even if they have the same contents. This means we need to switch to == in this case. Of course the only case when it is True both are actually the same object which is of course what I naively did in the tests. Sorry. Might consider doing a new release with this bug fix as soon as possible.

filefisher/filefisher/_filefinder.py

Lines 723 to 724 in f896d68

	if self.df.columns is not other.df.columns:
	raise ValueError("FileContainers must have the same keys.")

[mathause]

Good catch - also missed that in the review.