gh-75723: Idempotent .pth execution in site.addsitedir

[asottile]

• Issue: pth files in site-packages of venvs are executed twice #75723

[tcely]

@asottile

Do you have any ideas how to explain the test failure?

cpython/Lib/test/test_xmlrpc.py

Lines 479 to 489 in 4810bed

	class DateTimeTestCase(unittest.TestCase):
	def test_default(self):
	with mock.patch('time.localtime') as localtime_mock:
	time_struct = time.struct_time(
	[2013, 7, 15, 0, 24, 49, 0, 196, 0])
	localtime_mock.return_value = time_struct
	localtime = time.localtime()
	t = xmlrpclib.DateTime()
	self.assertEqual(str(t),
	time.strftime("%Y%m%dT%H:%M:%S", localtime))

---

   FAIL: test_default (test.test_xmlrpc.DateTimeTestCase.test_default)
   ----------------------------------------------------------------------
   Traceback (most recent call last):
     File "/Users/runner/Library/Developer/CoreSimulator/Devices/CED4C8DA-56B5-4FBF-A288-C5C2C197B3AD/data/Containers/Bundle/Application/4B219D99-CC21-4E94-B496-5F175FEC5822/iOSTestbed.app/python/lib/python3.15/test/test_xmlrpc.py", line 487, in test_default
       self.assertEqual(str(t),
       ~~~~~~~~~~~~~~~~^^^^^^^^
                        time.strftime("%Y%m%dT%H:%M:%S", localtime))
                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   AssertionError: '20260331T20:39:38' != '20130715T00:24:49'
   - 20260331T20:39:38
   + 20130715T00:24:49
   
   
   ----------------------------------------------------------------------
   Ran 93 tests in 27.345s
   
   FAILED (failures=1)
   test test_xmlrpc failed

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @FFY00 for commit 6c342df 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F147951%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[FFY00]

The test_xmlrpc failure on iOS only seems weird, I triggered a re-run.

[FFY00]

Well, the test is still failing. It seems like the time.localtime mock is not being installed in xmlrpc.client, or is losing the side effect after one call, weird.

I am gonna sync with main, just to be sure this is not a known issue.

[FFY00]

This looks okay, overall. There is just the test_xmlrpc failure we need to fix, and the news text that should be updated.

[FFY00]

Please re-write this to be more descriptive (eg. "Avoid re-executing .pth files when site.addsitedir is called for for a known directory")

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.