CI/TST: Check that unittest.mock is not being used in testing

[simonjayhawkins]

xref #24624 (comment)

[jreback]

ping on green.

[codecov]

Codecov Report

Merging #24648 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #24648      +/-   ##
==========================================
- Coverage   92.37%   92.37%   -0.01%     
==========================================
  Files         166      166              
  Lines       52377    52380       +3     
==========================================
+ Hits        48385    48386       +1     
- Misses       3992     3994       +2

Flag	Coverage Δ
#multiple	90.79% <ø> (-0.01%)	⬇️
#single	43.02% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/arrays/datetimes.py	97.68% <0%> (-0.16%)	⬇️
pandas/core/arrays/timedeltas.py	88.09% <0%> (-0.16%)	⬇️
pandas/core/arrays/period.py	98.52% <0%> (-0.02%)	⬇️
pandas/core/indexes/datetimelike.py	98.52% <0%> (ø)	⬆️

---

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[codecov]

Codecov Report

Merging #24648 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #24648      +/-   ##
==========================================
- Coverage   92.37%   92.37%   -0.01%     
==========================================
  Files         166      166              
  Lines       52377    52380       +3     
==========================================
+ Hits        48385    48386       +1     
- Misses       3992     3994       +2

Flag	Coverage Δ
#multiple	90.79% <ø> (-0.01%)	⬇️
#single	43.02% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/arrays/datetimes.py	97.68% <0%> (-0.16%)	⬇️
pandas/core/arrays/timedeltas.py	88.09% <0%> (-0.16%)	⬇️
pandas/core/arrays/period.py	98.52% <0%> (-0.02%)	⬇️
pandas/core/indexes/datetimelike.py	98.52% <0%> (ø)	⬆️

---

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[jreback]

thanks!

[plammens]

What was the rationale behind this? unittest.mock.Mock and unittest.mock.MagicMock are really useful (see this for example), and there's no equivalent with the monkeypatch fixture (which really only substitutes unittest.mock.patch, not the whole unittest.mock module).

If this was to avoid the import under Python 2, it's no longer relevant since Python 2 is no longer supported, and it should be reverted.

CC @simonjayhawkins, @jreback, @WillAyd

[jreback]

i think the description says it all

there is really no reason to use mock as monkey patch will do the limited things that we need

generally we prefer to not mock at all - when apis change often time mocks will work but the code is broken