CR fix

Author: pkch

mypy/semanal.py

@@ -3327,7 +3327,7 @@ def name_not_defined(self, name: str, ctx: Context) -> None:
     def name_already_defined(self, name: str, ctx: Context,
                              original_ctx: Optional[SymbolTableNode] = None) -> None:
         if original_ctx:
-            extra_msg = ' in line {}'.format(original_ctx.node.get_line())
+            extra_msg = ' on line {}'.format(original_ctx.node.get_line())
         else:
             extra_msg = ''
         self.fail("Name '{}' already defined{}".format(name, extra_msg), ctx)