GAPIC generator tests are flaky/broken

[jskeet]

#16862 is having trouble with the GAPIC generator tests, specifically "golden". From https://github.com/googleapis/google-cloud-python/actions/runs/25099156876/job/73547233794?pr=16862

************* Module redis_v1.services.cloud_redis.client
redis/google/cloud/redis_v1/services/cloud_redis/client.py:121:18: E0601: Using variable 'ASYNC_REST_EXCEPTION' before assignment (used-before-assignment)
Error: Process completed with exit code 2.