scipy probably not needed in [build-system.requires] table

[filip-komarzyniec]

Problem description

I believe that specifying scipy as a build-only dependency is unnecessary.

Pip builds the library in isolated environment (by default) where it first downloads (and alternatively builds) build-only dependencies. This behaviour creates additional problems for architectures for which there are not many .whl distributions, like e.g. ppc64le.

Steps/code/corpus to reproduce

1. create an environment where there is already an older scipy library version installed

cd gensim/
pip install . 

3. As there is no gensim .whl distribution for ppc64le, pip will try building gensim in a new isolated environment with build-only dependencies.
   As there is no scipy .whl distribution for ppc64le either, pip will try building that as well.
   Despite the fact that scipy is already installed in desired version within the target environment.
   Not only there will be a scipy version mismatch (pip will be building the latest version in the isolated environment) but it will also:
   • significantly prolong the install phase, as scipy takes relatively long to build from source,
   • create additional dependencies mess, as scipy build requires multiple other dependencies and system-level libraries

Desired resolution

I've tested locally installing gensim with modified pyproject.toml file (deleted scipy) and it works as expected.
Is there any other logic that does not allow deleting scipy as a build-only dependency?

Versions

gensim>4.3.*

[mpenkov]

Are you interested in making a PR @filip-komarzyniec ?

[filip-komarzyniec]

Sure, I'll be happy to, thanks!
I'll issue it shortly