Do not ignore error error when generating completion

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

Author: vdemeester

cmd/docker-app/completion.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
 	"github.com/spf13/cobra"
 )
@@ -18,8 +19,9 @@ To configure your bash shell to load completions for each session add to your ba
 # ~/.bashrc or ~/.profile
 . <(docker-app completion)
 `,
-		Run: func(cmd *cobra.Command, args []string) {
-			rootCmd.GenBashCompletion(dockerCli.Out())
+		Args: cli.NoArgs,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return rootCmd.GenBashCompletion(dockerCli.Out())
 		},
 	}
 }