The "means of egress" consists of three parts: exit access, exit and exit discharge.
Building code requires illumination (emergency lighting) to one footcandle for the entire means of egress including the exit discharge. (IBC 1006.1) There is no exception for rooms with only one exit door that I can find.
Your restroom would need lighting of at least one footcandle, just like the rest of the building. What doesn't need any lighting is rooms where no one is present, like a closet.
You may not need an emergency light in any specific room if light is dispersed through a window where emergency lighting is present, or other openings that would achieve the same effect.
One footcandle is not a lot of light. Cut a half-moon over the door, and you are OK.