On occasion I dive into the tmp dir from my build shell, forget I did that, then issue another bitbake command without backing out to the root build dir. Bitbake issues the following warning:

ERROR:  OE-core's config sanity checker detected a potential misconfiguration.
    Either fix the cause of this error or at your own risk disable the checker (see sanity.conf).
    Following is the list of potential problems / advisories:

    Please set a MACHINE in your local.conf or environment
Your version of local.conf was generated from an older version of local.conf.sample and there have been updates made to this file. Please compare the two files and merge any changes before continuing.
Matching the version numbers will remove this message.
"meld conf/local.conf conf/local.conf.sample" is a good way to visualise the changes.

ERROR: Execution of event handler 'check_sanity_eventhandler' failed

It would be nicer if it said:

"ERROR: bitbake must be run from the root buildir: /build/poky/fri2"

I believe this should be a relatively easy thing to test for prior to the sanity checker discovering there isn't a MACHINE defined (b/c there is no $CWD/conf/local.conf).