Minor cleanups in cli/command/container

This change does some minor cleanups in the
cli/command/container package;

- sort imports
- replace `fmt.Fprintf()` with `fmt.Fprintln()` if no formatting is used
- replace `fmt.Errorf()` with `errors.New()` if no formatting is used
- remove some redundant `else`'s

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

command/container/attach.go

@@ -1,18 +1,17 @@
 package container
 
 import (
-	"fmt"
+	"errors"
 	"io"
 	"net/http/httputil"
 
-	"golang.org/x/net/context"
-
 	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/cli"
 	"github.com/docker/docker/cli/command"
 	"github.com/docker/docker/pkg/signal"
 	"github.com/spf13/cobra"
+	"golang.org/x/net/context"
 )
 
 type attachOptions struct {
@@ -54,11 +53,11 @@ func runAttach(dockerCli *command.DockerCli, opts *attachOptions) error {
 	}
 
 	if !c.State.Running {
-		return fmt.Errorf("You cannot attach to a stopped container, start it first")
+		return errors.New("You cannot attach to a stopped container, start it first")
 	}
 
 	if c.State.Paused {
-		return fmt.Errorf("You cannot attach to a paused container, unpause it first")
+		return errors.New("You cannot attach to a paused container, unpause it first")
 	}
 
 	if err := dockerCli.In().CheckTty(!opts.noStdin, c.Config.Tty); err != nil {