URL format error checking
URL format error checking

Signed-off-by: Andrew Cornies <bc390b448e2f5e1596b428d488f03f278b5b6824@gmail.com>

ricardclau/packer,mitchellh/packer,rnaveiras/packer,rnaveiras/packer,pecigonzalo/packer,mitchellh/packer,rnaveiras/packer,hashicorp/packer,mitchellh/packer,mitchellh/packer,rnaveiras/packer,mitchellh/packer,pecigonzalo/packer,ricardclau/packer,hashicorp/packer,rnaveiras/packer,hashicorp/packer,pecigonzalo/packer,hashicorp/packer,ricardclau/packer,rnaveiras/packer,ricardclau/packer,pecigonzalo/packer,ricardclau/packer,ricardclau/packer