Package fails to install with pip 20.x

[Alexandros Nikolopoulos]

Tried to install directly from git via pip as follows:
-e git://github.com/clemfromspace/scrapy-selenium.git@master#egg=scrapy-selenium"

which fails with pip 20.2 as in the below trace. pip 18.x works fine

Traceback (most recent call last):
        from pip.download import PipSession
    ModuleNotFoundError: No module named 'pip.download'

    During handling of the above exception, another exception occurred:

    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "[redacted]\.env\src\scrapy-selenium\setup.py", line 10, in <module>
    ModuleNotFoundError: No module named 'pip._internal.download'
    ----------------------------------------
ERROR: Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.

[Hiromasa Ihara]

I also encountered the same problem.

[tristanlatr]

Is there a workaround for this issue ?
The best practice would be to have a static list of requirements, what's the need of the using pip internals ?

We can read in the pip documentation :
"Direct use of pip’s internals is not supported, and these internals can change at any time"