InvalidRequestError still happens

[skytreader]

Traceback (most recent call last):
  File "/home/chad/kode/alexandria/librarian/api.py", line 314, in edit_book
    form.illustrators.data)
  File "/home/chad/kode/alexandria/librarian/api.py", line 242, in edit_contrib
    db.session.add(contribution)
  File "/home/chad/.virtualenvs/alexandria/local/lib/python2.7/site-packages/sqlalchemy/orm/scoping.py", line 157, in do
    return getattr(self.registry(), name)(*args, **kwargs)
  File "/home/chad/.virtualenvs/alexandria/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1677, in add
    self._save_or_update_state(state)
  File "/home/chad/.virtualenvs/alexandria/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1696, in _save_or_update_state
    self._save_or_update_impl(st_)
  File "/home/chad/.virtualenvs/alexandria/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1995, in _save_or_update_impl
    self._update_impl(state)
  File "/home/chad/.virtualenvs/alexandria/local/lib/python2.7/site-packages/sqlalchemy/orm/session.py", line 1984, in _update_impl
    self.identity_map.add(state)
  File "/home/chad/.virtualenvs/alexandria/local/lib/python2.7/site-packages/sqlalchemy/orm/identity.py", line 134, in add
    orm_util.state_str(state), state.key))
InvalidRequestError: Can't attach instance <Role at 0x7fc7894f4ad0>; another instance with key (<class 'librarian.models.Role'>, (2L,)) is already present in this session.

Try doing this in a unit test: Have two books which will be edited to have an Illustrator modified. Editing the second book should throw this error.

In the meantime, a workaround is restarting the server. :(