Added comment about why we copy the whole method

lib/python/Products/Five/browser/pagetemplatefile.py

@@ -39,6 +39,9 @@ class ViewPageTemplateFile(viewpagetemplatefile.ViewPageTemplateFile):
     id = property(getId)
 
     def __call__(self, __instance, *args, **keywords):
+        # Work around BBB foul. Before Zope 2.12 there was no first argument
+        # but the Zope 3 version has one called instance. Some people used
+        # instance as an additional keyword argument.
         instance = __instance
         namespace = self.pt_getContext(
             request=instance.request,