The two issues were:
- The 1.2.6 release added a key argument to the Model class constructor that broke subclasses who were calling the constructor's private arguments with positional (not named) values. The fix is to restore the original ordering, and require that the new key argument be specified as a named argument only.
- The 1.2.6 release broke an interaction between remote_api and the local development app server.
There is no corresponding release for the Java language version of App Engine (the Java SDK remains at 1.2.6).