When compiled without OpenColorIO, Blender will first complain "Color
management: Error could not find role data role." before showing the
actual version number. This is now handled by looking for a "Blender "
prefix instead of just returning the first line of output.
This has as a side-effect that when no such line can be found, we know
it's not Blender, and thus an error can be returned (instead of the
version of whatever binary was being run).
