pseudo_step may lack the validation of yellow phase

[thinker310]

in world_sumo.py, class Intersection,
"if self.current_phase_time == self.yellow_phase_time:
self._change_phase(action)"
if current phase is green phase, then its current_phase_time reaches 3 (yellow_phase_time), the action is a new green phase, the current phase directly switch to new green phase, lack a yellow transition

[wingsweihua]

This issue seems to be fixed by the recent commit. Please let us know.