Lint check fails for generated samples

[parthea]

The lint check is failing on python-bigquery. See build log here from googleapis/python-bigquery#1129

I can reproduce the issue with the showcase code:

partheniou@partheniou:~/git/gapic-generator-python/test$ nox -s lint
nox > Running session lint
nox > Creating virtual environment (virtualenv) using python3.9 in .nox/lint
nox > python -m pip install flake8 black==19.10b0
nox > black --check docs google tests samples noxfile.py setup.py
All done! ✨ 🍰 ✨
75 files would be left unchanged.
nox > flake8 google tests samples
samples/generated_samples/localhost:7469_generated_showcase_v1beta1_echo_collect_sync_98a2221d.py:33:5: F841 local variable 'client' is assigned to but never used
samples/generated_samples/localhost:7469_generated_showcase_v1beta1_identity_delete_user_sync_7345a63e.py:39:5: F841 local variable 'response' is assigned to but never used
samples/generated_samples/localhost:7469_generated_showcase_v1beta1_echo_collect_sync_bb1f4448.py:33:5: F841 local variable 'client' is assigned to but never used
samples/generated_samples/localhost:7469_generated_showcase_v1beta1_identity_delete_user_async.py:39:5: F841 local variable 'response' is assigned to but never used
samples/generated_samples/localhost:7469_generated_showcase_v1beta1_echo_collect_async.py:33:5: F841 local variable 'client' is assigned to but never used
samples/generated_samples/localhost:7469_generated_showcase_v1beta1_identity_delete_user_sync_a45fe6ed.py:39:5: F841 local variable 'response' is assigned to but never used
nox > Command flake8 google tests samples failed with exit code 1
nox > Session lint failed.

[parthea]

Bumping to p1 as we want to merge autogenerated snippets downstream