Updated common/download.go to handle when a connection error happens (response is nil), and reformatted the error that's returned when an HTTP error occurs.
Updated common/download.go to handle when a connection error happens (response is nil), and reformatted the error that's returned when an HTTP error occurs.

tas50/packer,bryson/packer,grubernaut/packer,timsutton/packer,bryson/packer,rnaveiras/packer,youhong316/packer,hashicorp/packer,tb3088/packer,dave2/packer,hashicorp/packer,grubernaut/packer,pecigonzalo/packer,rnaveiras/packer,tb3088/packer,grubernaut/packer,dave2/packer,pecigonzalo/packer,rnaveiras/packer,bryson/packer,tas50/packer,dave2/packer,mkuzmin/packer,timsutton/packer,dave2/packer,mitchellh/packer,tb3088/packer,tas50/packer,youhong316/packer,bryson/packer,ricardclau/packer,mitchellh/packer,ricardclau/packer,ricardclau/packer,youhong316/packer,paulmey/packer,grubernaut/packer,paulmey/packer,dave2/packer,ricardclau/packer,bryson/packer,tas50/packer,timsutton/packer,rnaveiras/packer,pecigonzalo/packer,paulmey/packer,mitchellh/packer,mkuzmin/packer,ricardclau/packer,timsutton/packer,hashicorp/packer,mkuzmin/packer,grubernaut/packer,grubernaut/packer,timsutton/packer,rnaveiras/packer,paulmey/packer,bryson/packer,timsutton/packer,mkuzmin/packer,tb3088/packer,tas50/packer,youhong316/packer,dave2/packer,mkuzmin/packer,mitchellh/packer,youhong316/packer,paulmey/packer,pecigonzalo/packer,paulmey/packer,hashicorp/packer,rnaveiras/packer,mkuzmin/packer,tas50/packer,youhong316/packer,ricardclau/packer,tb3088/packer,mitchellh/packer,tb3088/packer