test: Making firewall test tolerant of GCE Enforcer. (#162)

* docs(samples): Making firewall test tolerant of GCE Enforcer.

* 🦉 Updates from OwlBot

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* 🦉 Updates from OwlBot

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* docs(samples): Marking the default values test as flaky.

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>

packages/google-cloud-compute/samples/snippets/requirements-test.txt

@@ -1,2 +1,3 @@
 pytest==6.2.5
+flaky==3.7.0
 google-cloud-storage==1.43.0

packages/google-cloud-compute/samples/snippets/test_sample_default_values.py

@@ -15,6 +15,7 @@
 import typing
 import uuid
 
+from flaky import flaky
 import google.auth
 import google.cloud.storage as storage
 import pytest
@@ -38,6 +39,7 @@ def temp_bucket():
     bucket.delete(force=True)
 
 
+@flaky(max_runs=3)
 def test_set_usage_export_bucket_default(
     capsys: typing.Any, temp_bucket: storage.Bucket
 ) -> None:

packages/google-cloud-compute/samples/snippets/test_sample_firewall.py

@@ -14,6 +14,7 @@
 import time
 import uuid
 
+import google.api_core.exceptions
 import google.auth
 from google.cloud import compute_v1
 import pytest
@@ -52,8 +53,15 @@ def firewall_rule():
 
     yield firewall_client.get(project=PROJECT, firewall=firewall_rule.name)
 
-    op = firewall_client.delete(project=PROJECT, firewall=firewall_rule.name)
-    op_client.wait(project=PROJECT, operation=op.name)
+    try:
+        op = firewall_client.delete(project=PROJECT, firewall=firewall_rule.name)
+        op_client.wait(project=PROJECT, operation=op.name)
+    except google.api_core.exceptions.BadRequest as err:
+        if err.code == 400 and "is not ready" in err.message:
+            # This means GCE enforcer has already deleted that rule.
+            pass
+        else:
+            raise err
 
 
 def test_create_delete():