Replace file with open, which is Python 3 compatible

Change-Id: I471ae9b372f88a508d4654b1a18c6da90397a828

glanceclient/shell.py

@@ -431,7 +431,7 @@ class OpenStackImagesShell(object):
                                                     force_auth=True)
                 schema = client.schemas.get("image")
 
-                with file(schema_file_path, 'w') as f:
+                with open(schema_file_path, 'w') as f:
                     f.write(json.dumps(schema.raw()))
             except Exception as e:
                 #NOTE(esheffield) do nothing here, we'll get a message later

glanceclient/v2/shell.py

@@ -29,7 +29,7 @@ def get_image_schema():
     if IMAGE_SCHEMA is None:
         schema_path = expanduser("~/.glanceclient/image_schema.json")
         if os.path.exists(schema_path) and os.path.isfile(schema_path):
-            with file(schema_path, "r") as f:
+            with open(schema_path, "r") as f:
                 schema_raw = f.read()
                 IMAGE_SCHEMA = json.loads(schema_raw)
     return IMAGE_SCHEMA