This is a reformulation of the ticket summary, after some discussion went on.

p_group_cohomology is divided into four parts:

• a C-library libmodres (autotoolized), also providing a data base.
• a pip-installable collection of Python / Cython modules
• some files containing GAP code (let's call it GAP helper module)
• a documentation using sphinx

Problem: Some of the modules refer to SAGE_LOCAL at installation or at run time, respectively. Moreover, the GAP helper module is currently installed into SAGE_LOCAL/share/sage, which has been removed.

Issues of each part:

• The C-library seems totally fine. One could consider to turn it into a stand-alone spkg.
• The Python / Cython modules seem mostly fine. Problems:
  • Its setup.py takes the job of installing the GAP helper module, in a folder whose location is determined from the value of SAGE_LOCAL and which actually doesn't exist any longer.
  • Some Python module makes GAP read the GAP helper module, thus also determines the import location from the value of SAGE_LOCAL.
    Proposed solution:
  • It shouldn't be the job of setup.py to install the GAP helper module.
  • It should be possible for GAP to load the helper module without explicitly constructing a path derived from SAGE_LOCAL.
    Side remark: It would be possible to move the Python / Cython modules into Sage's src tree, but that would created issues with testing and documentation.
• The files containing GAP code are not intended to be a proper GAP module, but should perhaps behave like a proper GAP module. A more or less clean solution would be to put it into GAP's pkg folder such that it can be loaded by LoadPackage("pGroupCohomologyHelpers");. Problem: How to determine GAP's pkg folder at installation time without referring to SAGE_LOCAL?
• Documentation is built using $MAKE html and then copied. It was suggested to replace cp -r by sdh_install.

Upstream of the package: https://github.com/sagemath/p_group_cohomology/releases/tag/v3.3.2

CC: @embray @jhpalmieri @orlitzky @kiwifb @dimpase

Component: packages: optional

Author: Simon King

Branch/Commit: f4e5f6a

Reviewer: Dima Pasechnik, Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/28711