Better error on attach no tty

Signed-off-by: John Howard <jhoward@microsoft.com>

api/client/cli.go

@@ -67,7 +67,11 @@ func (cli *DockerCli) CheckTtyInput(attachStdin, ttyMode bool) error {
 	// be a tty itself: redirecting or piping the client standard input is
 	// incompatible with `docker run -t`, `docker exec -t` or `docker attach`.
 	if ttyMode && attachStdin && !cli.isTerminalIn {
-		return errors.New("cannot enable tty mode on non tty input")
+		eText := "the input device is not a TTY"
+		if runtime.GOOS == "windows" {
+			return errors.New(eText + ".  If you are using mintty, try prefixing the command with 'winpty'")
+		}
+		return errors.New(eText)
 	}
 	return nil
 }

integration-cli/docker_cli_attach_test.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"os/exec"
+	"runtime"
 	"strings"
 	"sync"
 	"time"
@@ -103,7 +104,10 @@ func (s *DockerSuite) TestAttachTTYWithoutStdin(c *check.C) {
 			return
 		}
 
-		expected := "cannot enable tty mode"
+		expected := "the input device is not a TTY"
+		if runtime.GOOS == "windows" {
+			expected += ".  If you are using mintty, try prefixing the command with 'winpty'"
+		}
 		if out, _, err := runCommandWithOutput(cmd); err == nil {
 			done <- fmt.Errorf("attach should have failed")
 			return

integration-cli/docker_cli_exec_test.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"os/exec"
 	"reflect"
+	"runtime"
 	"sort"
 	"strings"
 	"sync"
@@ -182,7 +183,10 @@ func (s *DockerSuite) TestExecTTYWithoutStdin(c *check.C) {
 			return
 		}
 
-		expected := "cannot enable tty mode"
+		expected := "the input device is not a TTY"
+		if runtime.GOOS == "windows" {
+			expected += ".  If you are using mintty, try prefixing the command with 'winpty'"
+		}
 		if out, _, err := runCommandWithOutput(cmd); err == nil {
 			errChan <- fmt.Errorf("exec should have failed")
 			return

integration-cli/docker_cli_run_test.go

@@ -12,6 +12,7 @@ import (
 	"path/filepath"
 	"reflect"
 	"regexp"
+	"runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -2642,7 +2643,10 @@ func (s *DockerSuite) TestRunTTYWithPipe(c *check.C) {
 			return
 		}
 
-		expected := "cannot enable tty mode"
+		expected := "the input device is not a TTY"
+		if runtime.GOOS == "windows" {
+			expected += ".  If you are using mintty, try prefixing the command with 'winpty'"
+		}
 		if out, _, err := runCommandWithOutput(cmd); err == nil {
 			errChan <- fmt.Errorf("run should have failed")
 			return
@@ -2655,7 +2659,7 @@ func (s *DockerSuite) TestRunTTYWithPipe(c *check.C) {
 	select {
 	case err := <-errChan:
 		c.Assert(err, check.IsNil)
-	case <-time.After(6 * time.Second):
+	case <-time.After(30 * time.Second):
 		c.Fatal("container is running but should have failed")
 	}
 }