Add test for #15966

[watercrossing]

• adds test for BUG: comparing TZ-aware timestamps to a scalar results in exception #15966, but it has been fixed already
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry -- its only an added test?

[codecov]

Codecov Report

Merging #18170 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #18170      +/-   ##
==========================================
+ Coverage    91.4%    91.4%   +<.01%     
==========================================
  Files         163      163              
  Lines       50068    50068              
==========================================
+ Hits        45764    45767       +3     
+ Misses       4304     4301       -3

Flag	Coverage Δ
#multiple	89.21% <ø> (+0.02%)	⬆️
#single	40.33% <ø> (-0.06%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.8% <0%> (-0.1%)	⬇️
pandas/plotting/_converter.py	65.2% <0%> (+1.81%)	⬆️

---

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[codecov]

Codecov Report

Merging #18170 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #18170      +/-   ##
==========================================
+ Coverage    91.4%    91.4%   +<.01%     
==========================================
  Files         163      163              
  Lines       50068    50068              
==========================================
+ Hits        45764    45767       +3     
+ Misses       4304     4301       -3

Flag	Coverage Δ
#multiple	89.21% <ø> (+0.02%)	⬆️
#single	40.33% <ø> (-0.06%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.8% <0%> (-0.1%)	⬇️
pandas/plotting/_converter.py	65.2% <0%> (+1.81%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5350330...002da39. Read the comment docs.

[codecov]

Codecov Report

Merging #18170 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #18170      +/-   ##
==========================================
+ Coverage    91.4%    91.4%   +<.01%     
==========================================
  Files         163      163              
  Lines       50068    50068              
==========================================
+ Hits        45764    45767       +3     
+ Misses       4304     4301       -3

Flag	Coverage Δ
#multiple	89.21% <ø> (+0.02%)	⬆️
#single	40.33% <ø> (-0.06%)	⬇️

Impacted Files	Coverage Δ
pandas/io/gbq.py	25% <0%> (-58.34%)	⬇️
pandas/core/frame.py	97.8% <0%> (-0.1%)	⬇️
pandas/plotting/_converter.py	65.2% <0%> (+1.81%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5350330...002da39. Read the comment docs.

[TomAugspurger]

No need for a whatsnew, thanks @watercrossing.