Implement stream_read_file for the Swift storage engine

Note that Swift doesn't seem to have a file-like interface, so we need to wrap the generator we get back from it.

Fixes #210

storage/swift.py

@@ -1,6 +1,7 @@
 """ Swift storage driver. Based on: github.com/bacongobbler/docker-registry-driver-swift/ """
 from swiftclient.client import Connection, ClientException
 from storage.basestorage import BaseStorage
+from util.generatorfile import GeneratorFile
 
 from random import SystemRandom
 import string
@@ -8,6 +9,7 @@ import logging
 
 logger = logging.getLogger(__name__)
 
+
 class SwiftStorage(BaseStorage):
   def __init__(self, swift_container, storage_path, auth_url, swift_user,
                swift_password, auth_version=None, os_options=None, ca_cert_path=None):
@@ -143,7 +145,7 @@ class SwiftStorage(BaseStorage):
       yield data
 
   def stream_read_file(self, path):
-    raise NotImplementedError
+    return GeneratorFile(self.stream_read(path))
 
   def stream_write(self, path, fp, content_type=None, content_encoding=None):
     self._put_object(path, fp, self.buffer_size, content_type=content_type,