Bug 291902 – [AutoInstall] warn when a distribution package contains modules not defined as aliases

• Status: NEW
• Component: Tools / Tests

[Sam Sneddon [:gsnedders]]

Failing to declare what modules are provided by a given requirement can lead to surprising/broken behaviour. 

For example, from bug 290598:

```
  File "/Volumes/Data/sample.py", line 4, in <module>
    from attrs import define, field, evolve
  File "/Library/Python/3.9/site-packages/attrs/__init__.py", line 3, in <module>
    from attr import (
ImportError: cannot import name 'AttrsInstance' from 'attr' (/Users/buildbot/Library/webkitpy/autoinstalled/python-3-arm64/attr/__init__.py)
```

This is because we don't didn't know that `attrs` was provided by the `attr` requirement, and thus we didn't autoinstall it when we hit an import of `attrs`, instead falling back to the site-directory, but that then imported` attr`, and then we hit problems because we had multiple versions of `attrs` both imported.

[Radar WebKit Bug Importer]

<rdar://problem/149779392>