install-poetry fails with PIP_REQUIRE_VIRTUALENV

[neersighted]

Because install-poetry.py does not check the exit status of pip when bootstrapping the temporary virtualenv module, users are confronted with an odd error when they have $PIP_REQUIRE_VIRTUALENV set in their environment.

Output looks something like the following:

Installing Poetry...
Retrieving Poetry metadata

# Welcome to Poetry!

This will download and install the latest version of Poetry,
a dependency and package manager for Python.

It will add the `poetry` command to Poetry's bin directory, located at:

/home/neersighted/.local/share/pypoetry/bin

You can uninstall at any time by executing this script with the --uninstall option,
and these changes will be reverted.

Installing Poetry (1.1.6): Creating environment
Traceback (most recent call last):
  File "<stdin>", line 808, in <module>
  File "<stdin>", line 804, in main
  File "<stdin>", line 417, in run
  File "<stdin>", line 439, in install
  File "<stdin>", line 505, in make_env
AttributeError: module 'virtualenv' has no attribute 'cli_run'

This can easily be corrected by invoking the script again with PIP_REQUIRE_VIRTUALENV= to 'reset' the environmental variable.

For some background:
Pip provides this opt-in so that users can ensure they don't accidentally clutter or break their system installation of Python. Normally when this feature blocks execution of a command, it is called out to the user like this:

ERROR: Could not find an activated virtualenv (required).

Because pip is being invoked by install-poetry.py without checking exit status or output, this information is lost.

I would suggest explicitly resetting PIP_REQUIRE_VIRTUALENV in the installer script unconditionally to ensure that this interaction doesn't cause the failure above.

[neersighted]

The installer changes proposed in #4099 greatly simplify the virtualenv-related code and solve half this issue (unexplained errors/discarded information). Now we just have to determine if the installer breaking due to this setting is a bug, or if the user is responsible for unsetting it before running the installer.

Thoughts, @sdispater?

[neersighted]

I was wrong about this -- #4099 with actually entirely solve this issue as Poetry will no longer invoke pip outside a virtualenv! Nice!

[github-actions]

This issue has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.