The exceptions in bitbake_main() created by BBMainException() do not notify the user. It is a silent failure. An easy way to test this is by doing "bitbake --server-only" and notice that no error message appears. This regression appears to have been caused by commit 4e186596338af52bf720dcbbdd3a07b722cf9575.
This issue is hopefully fixed by this commit: http://lists.openembedded.org/pipermail/bitbake-devel/2015-April/005687.html Can you check please?
Should be fixed by this commit: http://cgit.openembedded.org/bitbake/commit/?id=c8e2a40c4e9865ebef9936d23644f2602a5c90f5