Fixed #21323 -- Improved readability of serialized Operation.

django/db/migrations/operations/base.py

@@ -21,6 +21,8 @@ class Operation(object):
     # Can this migration be represented as SQL? (things like RunPython cannot)
     reduces_to_sql = True
 
+    serialization_expand_args = []
+
     def __new__(cls, *args, **kwargs):
         # We capture the arguments to make returning them trivial
         self = object.__new__(cls)