Merge v1.2.1-master

Signed-off-by: Emile Vauge <emile@vauge.com>

vendor/github.com/Sirupsen/logrus/terminal_windows.go

@@ -3,11 +3,13 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build windows
+// +build windows,!appengine
 
 package logrus
 
 import (
+	"io"
+	"os"
 	"syscall"
 	"unsafe"
 )
@@ -19,9 +21,13 @@ var (
 )
 
 // IsTerminal returns true if stderr's file descriptor is a terminal.
-func IsTerminal() bool {
-	fd := syscall.Stderr
-	var st uint32
-	r, _, e := syscall.Syscall(procGetConsoleMode.Addr(), 2, uintptr(fd), uintptr(unsafe.Pointer(&st)), 0)
-	return r != 0 && e == 0
+func IsTerminal(f io.Writer) bool {
+	switch v := f.(type) {
+	case *os.File:
+		var st uint32
+		r, _, e := syscall.Syscall(procGetConsoleMode.Addr(), 2, uintptr(v.Fd()), uintptr(unsafe.Pointer(&st)), 0)
+		return r != 0 && e == 0
+	default:
+		return false
+	}
 }