Refs #14030 -- Removed more backwards compatiblity for old-style aggregates.

Per deprecation timeline.

django/db/models/aggregates.py

@@ -24,7 +24,6 @@ class Aggregate(Func):
                     before_resolved = self.get_source_expressions()[index]
                     name = before_resolved.name if hasattr(before_resolved, 'name') else repr(before_resolved)
                     raise FieldError("Cannot compute %s('%s'): '%s' is an aggregate" % (c.name, name, name))
-        c._patch_aggregate(query)  # backward-compatibility support
         return c
 
     @property
@@ -41,37 +40,6 @@ class Aggregate(Func):
     def get_group_by_cols(self):
         return []
 
-    def _patch_aggregate(self, query):
-        """
-        Helper method for patching 3rd party aggregates that do not yet support
-        the new way of subclassing. This method will be removed in Django 1.10.
-
-        add_to_query(query, alias, col, source, is_summary) will be defined on
-        legacy aggregates which, in turn, instantiates the SQL implementation of
-        the aggregate. In all the cases found, the general implementation of
-        add_to_query looks like:
-
-        def add_to_query(self, query, alias, col, source, is_summary):
-            klass = SQLImplementationAggregate
-            aggregate = klass(col, source=source, is_summary=is_summary, **self.extra)
-            query.aggregates[alias] = aggregate
-
-        By supplying a known alias, we can get the SQLAggregate out of the
-        aggregates dict, and use the sql_function and sql_template attributes
-        to patch *this* aggregate.
-        """
-        if not hasattr(self, 'add_to_query') or self.function is not None:
-            return
-
-        placeholder_alias = "_XXXXXXXX_"
-        self.add_to_query(query, placeholder_alias, None, None, None)
-        sql_aggregate = query.aggregates.pop(placeholder_alias)
-        if 'sql_function' not in self.extra and hasattr(sql_aggregate, 'sql_function'):
-            self.extra['function'] = sql_aggregate.sql_function
-
-        if hasattr(sql_aggregate, 'sql_template'):
-            self.extra['template'] = sql_aggregate.sql_template
-
 
 class Avg(Aggregate):
     function = 'AVG'