[storage] fix: use unique blob name (GoogleCloudPlatform#3568)

* [storage] fix: use unique blob name

fixes GoogleCloudPlatform#3567

* add some comments

Author: Takashi Matsuo

storage/cloud-client/encryption_test.py

@@ -15,7 +15,9 @@
 import base64
 import os
 import tempfile
+import uuid
 
+from google.api_core.exceptions import NotFound
 from google.cloud import storage
 from google.cloud.storage import Blob
 import pytest
@@ -54,18 +56,36 @@ def test_upload_encrypted_blob():
         )
 
 
-@pytest.fixture
+@pytest.fixture(scope="module")
 def test_blob():
     """Provides a pre-existing blob in the test bucket."""
     bucket = storage.Client().bucket(BUCKET)
+    blob_name = "test_blob_{}".format(uuid.uuid4().hex)
     blob = Blob(
-        "encryption_test_sigil",
+        blob_name,
         bucket,
         encryption_key=TEST_ENCRYPTION_KEY_DECODED,
     )
     content = "Hello, is it me you're looking for?"
     blob.upload_from_string(content)
-    return blob.name, content
+
+    yield blob.name, content
+
+    # To delete an encrypted blob, you have to provide the same key
+    # used for the blob. When you provide a wrong key, you'll get
+    # NotFound.
+    try:
+        # Clean up for the case that the rotation didn't occur.
+        blob.delete()
+    except NotFound as e:
+        # For the case that the rotation succeeded.
+        print("Ignoring 404, detail: {}".format(e))
+        blob = Blob(
+            blob_name,
+            bucket,
+            encryption_key=TEST_ENCRYPTION_KEY_2_DECODED
+        )
+        blob.delete()
 
 
 def test_download_blob(test_blob):