Error gracefully when an image is not found on pull. Addresses #50 and comments from #49

future/future.go

@@ -89,7 +89,7 @@ func Pv(src io.Reader, info io.Writer) io.Reader {
 // the body of the response. If `stderr` is not nil, a progress bar will be
 // written to it.
 func Curl(url string, stderr io.Writer) (io.Reader, error) {
-	curl := exec.Command("curl", "-#", "-L", url)
+	curl := exec.Command("curl", "-#", "-L", "--fail", url)
 	output, err := curl.StdoutPipe()
 	if err != nil {
 		return nil, err
@@ -98,5 +98,8 @@ func Curl(url string, stderr io.Writer) (io.Reader, error) {
 	if err := curl.Start(); err != nil {
 		return nil, err
 	}
+	if err := curl.Wait(); err != nil {
+		return nil, err
+	}
 	return output, nil
 }

server/server.go

@@ -428,12 +428,16 @@ func (srv *Server) CmdPull(stdin io.ReadCloser, stdout io.Writer, args ...string
 	}
 	fmt.Fprintf(stdout, "Downloading from %s\n", u.String())
 	// Download with curl (pretty progress bar)
-	// If curl is not available, fallback to http.Get()
+	// If curl is not available or receives a HTTP error, fallback
+	// to http.Get()
 	archive, err := future.Curl(u.String(), stdout)
 	if err != nil {
 		if resp, err := http.Get(u.String()); err != nil {
 			return err
 		} else {
+			if resp.StatusCode >= 400 {
+				return errors.New("Got HTTP status code >= 400: " + resp.Status)
+			}
 			archive = resp.Body
 		}
 	}