Fix accepting settings arguments to s3boto backend storage

storages/backends/s3boto.py

@@ -227,7 +227,7 @@ def __init__(self, acl=None, bucket=None, **settings):
         # check if some of the settings we've provided as class attributes
         # need to be overwritten with values passed in here
         for name, value in settings.items():
-            if name in self.__dict__:
+            if hasattr(self, name):
                 setattr(self, name, value)
 
         # For backward-compatibility of old differing parameter names