Python 3 testsuite fixes (Windows): commit and nominate for backport?

Hi devs, and Jun and Yasuhito in particular,

As I just posted in the "Subversion 1.14.0 up for testing/signing"
thread, I completed successful testruns with Python 3 on Windows (and
swig 4) , thanks to your recent fixes and patches in this area.

It would be good if all those outstanding patches could be committed,
and if all those fixes could be nominated for backport in
1.14.x/STATUS. They will certainly get my vote :-) ! Can you guys make
some time to wrap these up?

Quoting from the signing-thread, this is the complete list of trunk
revisions and patches that I applied:

> I applied the following fixes for known testsuite and (swig-)building issues:
>
> Merged from trunk, for building swig-python bindings with swig 4:
> - r1877338 (Fix differences of SWIG_PY_OPTS between Unix and Windows.
> Enable building with Swig 4)
>
> Merged from trunk, testsuite fixes for running the testsuite with Python 3:
> - r1876707 (Escape special characters in path when construct expected
> output regex.)
> - r1876734 (subversion/tests/cmdline/blame_tests.py (blame_youngest_to_oldest):
> Use svntest.main.file_write to avoid end of line conversion.)
> - r1877318 (Fix svnrdump tests on Windows with Python 3)
> - r1877712 (entries-dump: Escape string-typed attribute values when serializing
> them as Python string literals.)
>
> Applied following testsuite patches for running the testsuite with Python 3:
> - py38-windows-add-dll-directory--v2.diff posted by jun66j5 on
> 2020-05-11 in dev@ thread
> "[PATCH] fix unable to load *.pyd files with Python 3.8.x on Windows"
> - sain_keep_eol_style_win_patch_20200506.txt,
> fix_svnadmin_tests_patch.txt,
> fix_svndumpfilter_tests_patch.txt
> posted by futatuki on 2020-05-06 in dev@ thread
> "Problems running testsuite on Windows with Python 3"
> - Patch remove-uses-of-os-dup2.diff posted by jun66j5 on 2020-05-08 in
> dev@ thread
> "Problems running testsuite on Windows with Python 3"
> - Patch fix-entries-dump-patch.txt posted by futatuki on 2020-05-26 in
> dev@ thread
> "One more issue in tests on Windows with Python 3"

Thanks,

-- 
Johan