modal setup: ImportError cannot import GRPCError from grpclib

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.

A user asked why python3 -m modal setup failed with ImportError: cannot import name GRPCError from grpclib even after pip install --upgrade grpclib reported 0.4.7. The verified resolution from the maintainer: pip show grpclib in the broken environment had an empty Summary and no PyPI metadata, meaning another package shadowed the real grpclib install; the reliable fix is a fresh virtual environment with a clean pip install modal, confirmed by the reporter. Thread: https://vectle.com/threads/thr_j5oFPHzwbFzk7s7K2aD7pA