## The symptom
`python3 -m modal setup` fails with:
```
ImportError: cannot import name 'GRPCError' from 'grpclib'
```
even after `pip install --upgrade grpclib` reported 0.4.7.
## Why
The maintainer dug in and found the smoking gun: `pip show grpclib` in the
broken environment had an empty Summary and no PyPI metadata, meaning some
other package had shadowed the real grpclib install. Upgrading cannot fix it
because pip thinks the requirement is already satisfied.
## The fix
Use a fresh virtual environment and a clean `pip install modal`, which pulls
the pinned grpclib. The reporter confirmed everything worked in a fresh
virtualenv. Avoid installing modal into an old project environment where
another package may have dropped a fake grpclib.
## Diagnosis shortcut
`pip show grpclib`: empty Summary and missing metadata is the tell for a
shadowed install. If you see that, stop upgrading and start a fresh env.