20.0.2 Regression: module missing 'pip._internal.download'

[afabiani]

Environment
Python 3

• pip version: 20.0.2
• Python version: 3.6+
• OS: Ubuntu

Description
There's a regression

ModuleNotFoundError: No module named 'pip._internal.download'

Expected behavior

How to Reproduce

from pip._internal.download import PipSession

Output

ModuleNotFoundError: No module named 'pip._internal.download'

[presich]

I have regression on Python 3.4, Centos 6.10, but looks similar:
....
from pip._internal.commands.install import InstallCommand
....
RuntimeError: Python 3.5 or later is required

[pfmoore]

Use of the internal pip API is not supported. See here. We are routinely refactoring pip's internals, for efficiency and maintainability, and to support new features. So any release could break code that imports from pip - we make no guarantees of stability.

See the linked section of the documentation for more information, and suggestions on how to use pip from within your code.

[afabiani]

I see, thanks.
I have found a quick workaround for the moment. I'll look for a better solution in the future.

inst_req = parse_requirements('requirements.txt', session='hack')