xmlrpc: don't call xmlrpc methods twice! (#17712)

Author: ewdurbin

warehouse/legacy/api/xmlrpc/views.py

@@ -212,7 +212,7 @@ def faultString(self):  # NOQA: ignore=N802
 class TypedMapplyViewMapper(MapplyViewMapper):
     def mapply(self, fn, args, kwargs):
         try:
-            validate_call(fn)(*args, **kwargs)
+            return validate_call(fn)(*args, **kwargs)
         except ValidationError as exc:
             raise XMLRPCInvalidParamTypes(
                 "; ".join(
@@ -230,8 +230,6 @@ def mapply(self, fn, args, kwargs):
                 )
             )
 
-        return super().mapply(fn, args, kwargs)
-
 
 @view_config(route_name="xmlrpc.pypi", context=Exception, renderer="xmlrpc")
 def exception_view(exc, request):