fix: Fixed AttributeError when working with Blobs and Buckets

Fixes googleapis#540

google/cloud/storage/bucket.py

@@ -24,6 +24,7 @@
 from six.moves.urllib.parse import urlsplit
 
 from google.api_core import datetime_helpers
+from google.cloud import storage
 from google.cloud._helpers import _datetime_to_rfc3339
 from google.cloud._helpers import _NOW
 from google.cloud._helpers import _rfc3339_nanos_to_datetime
@@ -610,7 +611,7 @@ def __init__(self, client, name=None, user_project=None):
         """
         name = _validate_name(name)
         super(Bucket, self).__init__(name=name)
-        self._client = client
+        self._client = client or storage.Client()
         self._acl = BucketACL(self)
         self._default_object_acl = DefaultObjectACL(self)
         self._label_removals = set()