Better error message with failing discovery #2493
Description
What's the problem this feature will solve?
pre-commit failed due to StopIteration. Investigation shows that this is caused by an error thrown by virtualenv. See below for full trace when attempting to construct a virtual environment. Through discussion on the virtualenv discord, this closed issue was suggested as related: #2176
Investigation strongly suggested that the issue was indeed related. Pip uninstalling all packages and reinstalling only virtualenv allowed for creation of the virtual environment. pip list before uninstalling shows that there were some horribly out of date packages for the python version used. Removing or updating the packages fixed the issue.
Describe the solution you'd like
While I was able to identify and fix the issue with a bit of help from the virtualenv community, the error was cryptic and did not provide information about what problem was or what steps could be taken to solve it.
I am not familiar with the discovery process, but a message stating which package or path was causing the issue would be helpful. Perhaps:
> python -m virtualenv my_venv
Error: package discovery failed for <packageName>. Please check for package updates.
Alternative Solutions
pip list -o does show the installed and latest version of all packages which was able to help me find which were significantly out of date, but this is a partial solution unless a user knows that other packages are the issue. Adding a note to the Users Guide may be helpful.
This is the current output (with full traceback):
> python -m virtualenv --with-traceback my_venv
Traceback (most recent call last):
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\runpy.py", line 196, in _run_module_as_main
return _run_code(code, main_globals, None,
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\runpy.py", line 86, in _run_code
exec(code, run_globals)
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\site-packages\virtualenv\__main__.py", line 69, in <module>
run_with_catch() # pragma: no cov
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\site-packages\virtualenv\__main__.py", line 54, in run_with_catch
run(args, options, env)
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\site-packages\virtualenv\__main__.py", line 16, in run
session = cli_run(args, options, env)
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\site-packages\virtualenv\run\__init__.py", line 28, in cli_run
of_session = session_via_cli(args, options, setup_logging, env)
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\site-packages\virtualenv\run\__init__.py", line 46, in session_via_cli
parser, elements = build_parser(args, options, setup_logging, env)
File "C:\ANSYSDev\develop\Core_Dependencies\CPython\3_10\winx64\Release\python\lib\site-packages\virtualenv\run\plugin\discovery.py", line 20, in get_discover
default=next(iter(choices)),
StopIteration