If BBPATH isn't set and bblayers.conf isn't found, improve the message
shown to the user to help their understanding of what the problem might
be.
[YOCTO #3271]
(Bitbake rev: 0e639f5cbc813c8d4719019cfdd4287e9a429610)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
A