TWEAK: Use helper func for API errors.
TWEAK: Use helper func for API errors.

hoffmabc/openbazaar-go,hoffmabc/openbazaar-go,OpenBazaar/openbazaar-go,OpenBazaar/openbazaar-go,OpenBazaar/openbazaar-go,hoffmabc/openbazaar-go,gubatron/openbazaar-go,gubatron/openbazaar-go,gubatron/openbazaar-go