The error sounds like its being caused by some mission scripting trying to set some campaign variables.
The easiest way to solve this is that unless its part of a campaign and requires some scripting, just remove the mission.py file, and put any scripting you may have or need (such as setting lighting etc...) in the danger.py file (this is the danger room script).
As for the imports at the top.
This is a basic example of all you really should need (change the lighting values to your own)
from cshelper import *
from js import *
def OnPostInitMap():
Mission_SetSunlight(-100,70,0.5,0.5,(0.7,0.6,0.6))
Mission_SetShadows(-140,70,(0.2,0.2,0.4))
Mission_SetProjShadowBackground((1,1,1))
Mission_SetProjShadowColor((.6,.6,.6,1))