Filesystem bt5 Extension are stored as strings in bt5 (backward compatibility).

product/ERP5/Document/BusinessTemplate.py

@@ -3792,8 +3792,14 @@ class ExtensionTemplateItem(FilesystemToZodbTemplateItem):
         obj.text_content = f.read()
 
   def export(self, context, bta, **kw):
-    path = self.__class__.__name__
+    path = self.__class__.__name__ + '/'
     for key, obj in self._objects.iteritems():
+      # Back compatibility with filesystem Extensions
+      if isinstance(obj, str):
+        if not key.startswith(path):
+          key = path + key
+        bta.addObject(obj, name=key, ext='.py')
+      else:
         obj = obj._getCopy(context)
 
         f = StringIO(obj.text_content)