The sdk.py file calls functions from bb.utils and it just assumes it worked, never checks for return codes nor tries to catch exceptions.
related to bug: extensible SDK: silent error when using ipk packaging https://bugzilla.yoctoproject.org/show_bug.cgi?id=8180
Patch waiting to be merged in: http://lists.openembedded.org/pipermail/openembedded-core/2015-October/111715.html and in poky-contrib::remotes/contrib/besquive/sdk-return http://git.yoctoproject.org/cgit/cgit.cgi/poky-contrib/log/?h=besquive/sdk-return
Merged in oe-core 2e81dbdce6f92908c4d4c980af032516581178de.
Verified with 2.0.1: jethro/dd0ba9ea4a11ab15348d4fe3574e4b28784db82f