BUG: Assert_frame_equal always raising AssertionError when comparing extension dtypes

[phofl]

• closes BUG: pd.testing.assert_frame_equal(..., check_exact=True) raises AssertionError when comparing numeric ExtensionDtypes #39410
• tests added / passed
• Ensure all linting tests pass, see here for how to run them
• whatsnew entry

[jbrockmendel]

LGTM pending green

[jreback]

thanks @phofl

[jreback]

@meeseeksdev backport 1.2.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

$ git checkout 1.2.x
$ git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

$ git cherry-pick -m1 201d263aefecabc84ee49add65f37d06b45966e9

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

$ git commit -am 'Backport PR #39423: BUG: Assert_frame_equal always raising AssertionError when comparing extension dtypes'

4. Push to a named branch :

git push YOURFORK 1.2.x:auto-backport-of-pr-39423-on-1.2.x

5. Create a PR against branch 1.2.x, I would have named this PR:

"Backport PR #39423 on branch 1.2.x"

And apply the correct labels and milestones.

Congratulation you did some good work ! Hopefully your backport PR will be tested by the continuous integration and merged soon!

If these instruction are inaccurate, feel free to suggest an improvement.

[jreback]

cc @phofl if you wouldn't mind doing the backport here

[phofl]

Done