Pip=20.2 break packages installing on pypy

Environment

• pip version: 20.2
• Python version:

Python 2.7.13 (7.3.1+dfsg-2~ppa1~ubuntu16.04, Apr 23 2020, 03:08:28)                                                           
[PyPy 7.3.1 with GCC 5.4.0 20160609]

• OS: tested on linux

Description If you try to install any package with pip install, you will have follow stacktrace:

ERROR: Exception:
Traceback (most recent call last):
  File "/home/dsp25no/.pypyenv/site-packages/pip/_internal/cli/base_command.py", line 216, in _main
    status = self.run(options, args)
  File "/home/dsp25no/.pypyenv/site-packages/pip/_internal/cli/req_command.py", line 182, in wrapper
    return func(self, options, args)
  File "/home/dsp25no/.pypyenv/site-packages/pip/_internal/commands/install.py", line 421, in run
    pycompile=options.compile,
  File "/home/dsp25no/.pypyenv/site-packages/pip/_internal/req/__init__.py", line 90, in install_given_reqs
    pycompile=pycompile,
  File "/home/dsp25no/.pypyenv/site-packages/pip/_internal/req/req_install.py", line 831, in install
    requested=self.user_supplied,
  File "/home/dsp25no/.pypyenv/site-packages/pip/_internal/operations/install/wheel.py", line 829, in install_wheel
    requested=requested,
  File "/home/dsp25no/.pypyenv/site-packages/pip/_internal/operations/install/wheel.py", line 703, in _install_wheel
    assert os.path.exists(pyc_path)
AssertionError

Expected behavior Success package installation with 0 return code.

How to Reproduce

1. Install pypy
2. Reproduce

pip wheel pip
virtualenv .pypyenv -p pypy
source .pypyenv/bin/activate
pypy pip-20.2-py2.py3-none-any.whl/pip install --force pip

More info Regression happened in commit 2ece73cc862b8637b9d0da193f5a591fa6d1a2a2. compileall in Cpython generate compile files with names expected in function pyc_output_path, but with pypy filenames will be another, like __pycache__/__init__.pypy-73.pyc

[chrahunt]

Is there a fully compatible mechanism to get the pyc file path that would be generated for a file? I see:

• importlib.util.cache_from_source was introduced in 3.4.
• imp.cache_from_source doesn’t state an introduction version, but the Python 2 docs for imp don’t mention it (and it’s not present in my local 2.7.17).

I checked with pypy2.7-7.3.1 (on Linux), but it doesn’t look like either is backported.

PEP 3147 (introduced __pycache__) also mentions a mechanism for detecting whether PEP 3147 is available:

import imp
hasattr(imp, 'get_tag')

which returned False for me on the same version of pypy.

[hexagonrecursion]

This issue is marked as “python 2 only”. pip 21.0 dropped support for Python 2. Should this be closed?