Better error handling for GCS credential argument addition
Better error handling for GCS credential argument addition

Signed-off-by: Andrey Kostov <26ec56b3a284a8225458470ec1b0406a78360247@gmail.com>

yuwaMSFT2/distribution,docker/distribution,sergeyfd/distribution,sergeyfd/distribution,thaJeztah/distribution,dmcgowan/distribution,yuwaMSFT2/distribution,estesp/distribution,estesp/distribution,dmcgowan/distribution,sadlil/distribution,thaJeztah/distribution,sadlil/distribution,docker/distribution