Incorrect TypeError in FiniteStateMachine.add_from_transition_function

[cheuberg]

A TypeError? occurring in the callback function sage.combinat.finite_state_machine.FiniteStateMachine.add_from_transition_function is incorrectly caught and leads to a misleading ValueError?. Old behaviour:

sage: def transition(state, where):
sage: ...    return (vector([0,0]),1)
sage: Transducer(transition, input_alphabet=[0], initial_states=[0])
Traceback (click to the left of this block for traceback)
...
ValueError: The callback function for add_from_transition is expected to
return a pair (new_state, output_label) or a list of such pairs. For the
state 0 and the input letter 0, it however returned [((0, 0), 1)], which
is not acceptable.

New behaviour:

sage: def transition(state, where):
sage: ...    return (vector([0,0]),1)
sage: Transducer(transition, input_alphabet=[0], initial_states=[0])
Traceback (click to the left of this block for traceback)
...
TypeError: mutable vectors are unhashable

[dkrenn]

everything looks fine, doctests pass, docu checked, coverage checked