chore(deps): update dependency cryptography to v2.8 (#2655)

* chore(deps): update dependency cryptography to v2.8

Author: renovate-bot

iot/api-client/gcs_file_to_device/gcs_send_to_device_test.py

@@ -56,7 +56,10 @@ def test_blob():
     yield blob
 
     # Clean up
-    blob.delete()
+    try:
+        blob.delete()
+    except:  # noqa
+        pass
 
 
 @mock.patch('google.cloud.storage.client.Client.create_bucket')

iot/api-client/gcs_file_to_device/requirements.txt

@@ -4,6 +4,6 @@ google-auth-httplib2==0.0.3
 google-cloud-iot==0.3.0
 google-cloud-pubsub==1.0.0
 google-cloud-storage==1.19.1
-cryptography==2.7
+cryptography==2.8
 paho-mqtt==1.4.0
 pyjwt==1.7.1

iot/api-client/mqtt_example/requirements.txt

@@ -1,4 +1,4 @@
-cryptography==2.7
+cryptography==2.8
 flaky==3.6.1
 gcp-devrel-py-tools==0.0.15
 google-api-python-client==1.7.11