If you place a multiconfig which isn't enabled into an mcdepends you currently
get a traceback from runqueue. We can do better, add some code to tell the user
what happened in a more readable way without the traceback.
[YOCTO #14970]
(Bitbake rev: a4693b70764bb394ee2cf8dd12a5f6fce866008b)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>