don't use distutils.dir_util in copy_dir

[boegel]

fixes #3306

[Flamefire]

May I suggest not to switch implementations based on Python version? Why not use a single implementation which behaves as the Python 3.8 version always? Or a defined subset of it. I see no advantage of the usage of Python 3.8 function if a hand-rolled version must still exist. Just makes the test-surface larger

[lexming]

Tests with this PR can be found in easybuilders/easybuild-easyblocks#2049

[boegel]

May I suggest not to switch implementations based on Python version? Why not use a single implementation which behaves as the Python 3.8 version always? Or a defined subset of it. I see no advantage of the usage of Python 3.8 function if a hand-rolled version must still exist. Just makes the test-surface larger

The idea is that we can get rid of our own code whenever we reach only having to support Python 3.8 & newer...

I sort of see your point though.

Thoughts on this @lexming?

[lexming]

@boegel If our own implementation for Python < 3.8 works just as well in Python 3.8 and onwards, we could indeed use it indiscriminately.

[boegel]

@lexming I reproduced your broken use case in the tests and fixed it in e086444; special handling for Python >= 3.8 removed in 3c80fef

[lexming]

New tests in easybuilders/easybuild-easyblocks#2049 (comment)

[lexming]

LGTM

[lexming]

LGTM

All tests were fine, covering all current use cases (overwrite and merging) and directories with regular files and symlinks.

[lexming]

Going in, thanks @boegel !