Environment details

Pubsub: google-cloud-pubsub 1.0.2

Python 3.6.3

Google App Engine flex python

Steps to reproduce

google-cloud-pubsub requires the grpcio package w/o locking a specific version.

On April 3rd a new grpcio version was released w/o a pre-compiled wheel - v 1.28.1

Since the new grpcio package release, GAE flex python deploys (using GAE default image) requiring google-cloud-pubsub are timing out because the grpcio package is being compiled during deploy time - which takes 8+ minutes.

google-cloud-pubsub should either lock to a specific grpcio version - one with a compiled wheel - or use a relevant pip flag to make sure it uses the latest compiled wheel available.

Doesn't make sense for GAE deploys to timeout because of this.
IssueTracker was opened here: https://issuetracker.google.com/issues/153468670