gh-145754: Update signature retrieval in unittest.mock to use forwardref annotation format

[mschoettle]

Uses annotation format FORWARDREF instead of the default VALUE when calling inspect.signature.
STRING also seems to work but affects existing tests that check the signature.

• Issue: Autospeccing with unittest.mock is less robust with PEP 649 #145754

Closes#145754

[bedevere-app]

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[JelleZijlstra]

This change looks right to me, please add a unit test and we'll hopefully get it merged!

[mschoettle]

This change looks right to me, please add a unit test and we'll hopefully get it merged!

Thanks, @JelleZijlstra! I added a unit test. Are you able to review it or does it require @cjw296 as the code owner?

[JelleZijlstra]

Sorry, looks like I never submitted this review.

I am comfortable merging this once I'm happy with the code.

[miss-islington-app]

Thanks @mschoettle for the PR, and @JelleZijlstra for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[bedevere-app]

GH-146191 is a backport of this pull request to the 3.14 branch.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot x86 Debian Non-Debug with X 3.x (no tier) has failed when building commit d357a7d.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1245/builds/7793) and take a look at the build logs.
4. Check if the failure is related to this commit (d357a7d) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1245/builds/7793

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/contextlib.py"�[0m, line �[35m85�[0m, in �[35minner�[0m
return func(*args, **kwds)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m597�[0m, in �[35mtest_interrupt�[0m
exitcode =self._kill_process(multiprocessing.Process.interrupt)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/contextlib.py"�[0m, line �[35m85�[0m, in �[35minner�[0m
return func(*args, **kwds)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m578�[0m, in �[35m_kill_process�[0m
self.assertEqual(�[31mjoin�[0m�[1;31m()�[0m, None)
�[31m~~~~�[0m�[1;31m^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m251�[0m, in �[35m__call__�[0m
return �[31mself.func�[0m�[1;31m(*args, **kwds)�[0m
�[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/multiprocessing/process.py"�[0m, line �[35m156�[0m, in �[35mjoin�[0m
res =self._popen.wait(timeout)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/multiprocessing/popen_fork.py"�[0m, line �[35m44�[0m, in �[35mwait�[0m
return �[31mself.poll�[0m�[1;31m(os.WNOHANGif timeout ==0.0else0)�[0m
�[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/multiprocessing/popen_fork.py"�[0m, line �[35m28�[0m, in �[35mpoll�[0m
pid, sts = �[31mos.waitpid�[0m�[1;31m(self.pid, flag)�[0m
�[31m~~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m574�[0m, in �[35mhandler�[0m
raiseRuntimeError('join took too long: %s'% p)
�[1;35mRuntimeError�[0m: �[35mjoin took too long: <Process name='Process-1' pid=12129 parent=12127 started daemon>�[0m
Traceback (most recent call last):
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/contextlib.py"�[0m, line �[35m85�[0m, in �[35minner�[0m
return func(*args, **kwds)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m597�[0m, in �[35mtest_interrupt�[0m
exitcode =self._kill_process(multiprocessing.Process.interrupt)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/contextlib.py"�[0m, line �[35m85�[0m, in �[35minner�[0m
return func(*args, **kwds)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m578�[0m, in �[35m_kill_process�[0m
self.assertEqual(�[31mjoin�[0m�[1;31m()�[0m, None)
�[31m~~~~�[0m�[1;31m^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m251�[0m, in �[35m__call__�[0m
return �[31mself.func�[0m�[1;31m(*args, **kwds)�[0m
�[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/multiprocessing/process.py"�[0m, line �[35m156�[0m, in �[35mjoin�[0m
res =self._popen.wait(timeout)
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/multiprocessing/popen_fork.py"�[0m, line �[35m44�[0m, in �[35mwait�[0m
return �[31mself.poll�[0m�[1;31m(os.WNOHANGif timeout ==0.0else0)�[0m
�[31m~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/multiprocessing/popen_fork.py"�[0m, line �[35m28�[0m, in �[35mpoll�[0m
pid, sts = �[31mos.waitpid�[0m�[1;31m(self.pid, flag)�[0m
�[31m~~~~~~~~~~�[0m�[1;31m^^^^^^^^^^^^^^^^�[0m
File �[35m"/buildbot/buildarea/3.x.ware-debian-x86.nondebug/build/Lib/test/_test_multiprocessing.py"�[0m, line �[35m574�[0m, in �[35mhandler�[0m
raiseRuntimeError('join took too long: %s'% p)
�[1;35mRuntimeError�[0m: �[35mjoin took too long: <Process name='Process-158' pid=21989 parent=19679 started daemon>�[0m