MAINT: Remove self.assertFalse from testing

[gfyoung]

Title is self-explanatory.

Partially addresses #15990.

[jorisvandenbossche]

One remark for this replacement: in certain cases it might be that we want to test that something is actually False, and not falsey (for which you would need to do assert xx is False instead of assert not xx)
But, this is difficult to say without looking in more detail into each of the tests, which is a bit too much work ..

[gfyoung]

@jorisvandenbossche : Well according to unittest documentation, assertFalse(expr) checks that bool(expr) is False, so I think that concern might be moot.

[jorisvandenbossche]

Ah, you're correct. The implementation actually just does if expr: raise .., which is equivalent.

[max-sixty]

@gfyoung you're a hero for running through all these!

[gfyoung]

@MaximilianR : Thanks! Couldn't do it without bash ;)

[codecov]

Codecov Report

Merging #16151 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #16151   +/-   ##
=======================================
  Coverage   90.83%   90.83%           
=======================================
  Files         159      159           
  Lines       50796    50796           
=======================================
  Hits        46143    46143           
  Misses       4653     4653

Flag	Coverage Δ
#multiple	88.62% <ø> (ø)	⬆️
#single	40.31% <ø> (ø)	⬆️

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[jreback]

thanks!