Better error for mypy -p package without py.typed

[jogo-openai]

Improve the error message when running mypy -p packagename with a
package that doesn't have py.typed set.

package 'example' is skipping due to missing py.typed marker. See https://mypy.readthedocs.io/en/stable/installed_packages.html for more details

Fix #17048

[hauntsaninja]

Nice! Looking at find_modules_recursive, I think we can be a little more helpful. if not p_targets, let's call find_module directly, if the module not found reason is found without type hints, we can confidently say py.typed is missing (and otherwise we can fail with the existing message)

[jogo-openai]

test failure seems to be unrelated and not sure how to retry it

[hauntsaninja]

Don't worry about it, I'll take care of that :-)

Thanks again for the improvement!

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅