bpo-34182: Fix test_pydoc running as a script

[bbayles]

This PR fixes running test_pydoc as a module. The issue was that this line was returning Lib instead of /path/to/Lib.

$ ./python Lib/test/test_pydoc.py 
...
test_mixed_case_module_names_are_lower_cased (__main__.PydocDocTest) ... ok
...

----------------------------------------------------------------------
Ran 53 tests in 3.177s

OK (skipped=3)

https://bugs.python.org/issue34182

[serhiy-storchaka]

Running the test with the following command line still failed.

$ ./python Lib/test/./test_pydoc.py

[bbayles]

OK, I moved the abspath call to fix that.

[serhiy-storchaka]

Redundant parenthesis.

[miss-islington]

Thanks @bbayles for the PR, and @serhiy-storchaka for merging it 🌮🎉.. I'm working now to backport this PR to: 2.7, 3.6, 3.7.
🐍🍒⛏🤖

[bedevere-bot]

GH-8557 is a backport of this pull request to the 3.7 branch.

[miss-islington]

Sorry, @bbayles and @serhiy-storchaka, I could not cleanly backport this to 3.6 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 4e11c461ed39085b8495a35c9367b46d8a0d306d 3.6

[miss-islington]

Sorry, @bbayles and @serhiy-storchaka, I could not cleanly backport this to 2.7 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 4e11c461ed39085b8495a35c9367b46d8a0d306d 2.7

[bbayles]

I don't think the backport is necessary for 3.6 or 2.7. They both use os.path.realpath, which avoids the issue here.

The issue was introduced in ebfaa71 in 2017.

I think leaving 3.6 and 2.7 as they are leaves them vulnerable to 32031, however. Should I move this fix to those branches, or not bother?

[serhiy-storchaka]

This is not very important issue in any case.

[serhiy-storchaka]

Thank you for your PR!