pip-20.3b1 interprets httpie 'requests[socks]>=2.22.0' requirement differently than "legacy-resolver"

This is by no mean an exact timing test. I hope I kept enough exact comparison environment.



pip-20.3.0b1 takes at least (if it goes till the end) twice more time on below example.

Is it supposed to work well with "--pre  --no-index --trusted-host=None  --find-links=a_local_directory" ?

**Is the option "--pre" still valid ?**



I'm preparing Winptyhon builds using a local wheel directory  "C:\WinP\packages.srcreq"





I install the attached requirement "Cod_requirements64.txt" on a Python-3.9.0.1 64 bit Windows using:

- either pip-20.2.4 standard,

- either pip20.3.0b1 standard



intruction is  

`pip install --pre  --no-index --trusted-host=None  --find-links=C:\WinP\packages.srcreq  -r requirements.txt`



Result with pip-20.2.4:

- installed packages = attached file "pip_20.2.4_installed_package_result.txt"

- time taken : 14 minutes

- pip check : "No broken requirements found." 



Result with pip-20.3.b1:

- looking in lib \site_packages: 

    - nothing but was showing up in "Lib\Site-packages"  after 35' (so I stopped)

    - output is in "pip-20.3.0b1_too_long_test_output.txt"

[Cod_requirements64.txt](https://github.com/pypa/pip/files/5506798/Cod_requirements64.txt)

[pip-20.3.0b1_too_long_test_output.txt](https://github.com/pypa/pip/files/5506799/pip-20.3.0b1_too_long_test_output.txt)

[pip_20.2.4_installed_package_result.txt](https://github.com/pypa/pip/files/5506801/pip_20.2.4_installed_package_result.txt)



Addendum of november 11th: after resolution of the problem, speed of Pip-20.3 master is roughly 15' to install WinPython packages, pretty much equal to previous resolver.

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