Real Time Mirror -- Blender 3D Game Engine

11.  Add a string Property named material to the Mirror
Property must be named material.  Can't be named Fred or Material or anything else. The python code looks for a Property attached to the Mirror named material.

Add Property named material to the Mirror
Buttons Window menu >> Logic (F4)
Add Property button
Type:  String
Name:  material
Enter unique name you gave material

12.  Connect the Always Sensor to the Python Controller 

Mirror selected:  Object Mode

Buttons Window menu >> Logic (F4)
Pull wire from brass bump to brass dimple