... 
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
  File "model/db.py", line 18, in __exit__
    session.commit()
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/session.py", line 801, in commit
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/session.py", line 392, in commit
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/session.py", line 372, in _prepare_impl
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/session.py", line 2015, in flush
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/session.py", line 2133, in _flush
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/langhelpers.py", line 60, in __exit__
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/session.py", line 2097, in _flush
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/unitofwork.py", line 373, in execute
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/unitofwork.py", line 529, in execute
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/persistence.py", line 160, in save_obj
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/langhelpers.py", line 747, in __get__
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/orm/mapper.py", line 2652, in _sorted_tables
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/sql/ddl.py", line 989, in sort_tables
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/sql/ddl.py", line 1067, in sort_tables_and_constraints
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/sql/ddl.py", line 1067, in sort_tables_and_constraints
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/topological.py", line 50, in sort
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/topological.py", line 39, in sort_as_subsets
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/_collections.py", line 458, in difference_update
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/_collections.py", line 458, in difference_update
......
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/_collections.py", line 458, in difference_update
  File "/home/minecraft/lib/sqlalchemy.jar/sqlalchemy/util/_collections.py", line 458, in difference_update
RuntimeError: maximum recursion depth exceeded (Java StackOverflowError)