add link to pdb source (closes #22528)
merge 3.4 (#22528)
Prepare sphinx extensions for 1.3.
merge with 3.4
Dont define an empty SPHINXOPTS, which overrides a definition from the environment.
merge with 3.4
Move Doc/tools/sphinxext content to Doc/tools, there is no need for the nested subdirectory anymore.
Move Doc/tools/sphinxext content to Doc/tools, there is no need for the nested subdirectory anymore.
merge with 3.4
Issue 22465: grammar, number agreement.
Merge with 3.4
Issue #22333: Extend timeout in test_threaded_import

Check if the sporadic failure is related to a timeout.
The test just failed on the buildbot "x86 Windows7 3.x": 1 thread done / 20
(the 'done' condition was not signaled because 1 < 20).
Issue #22333: test_threaded_import now displays elapsed time in verbose mode.