Mouse instance named Despereaux, because literary references.

Despereaux

        else:
            despereaux = Mouse(initial_cell)
            done = False
            visited_cells = []
            route = MazeRoute()
            while (despereaux.can_travel() and
                   not despereaux.current_cell in visited_cells):
                if despereaux.current_cell in self._cells:
                    visited_cells.append(despereaux.current_cell)
                else:
                    route.add_cells([])
                    return route

            route.add_cells(visited_cells)
            return route