Check for terminal on both stdout and stderr

Author: José Valim

bin/elixir

@@ -85,8 +85,7 @@ if [ "$OSTYPE" = "cygwin" ]; then SCRIPT_PATH=$(cygpath -m $SCRIPT_PATH); fi
 if [ "$MODE" != "iex" ]; then ERL="-noshell -s elixir start_cli $ERL"; fi
 
 # Check for terminal support
-test -t 1
-if [ $? = 0 ]; then ERL="-elixir ansi_enabled true $ERL"; fi
+if test -t 1 -a -t 2; then ERL="-elixir ansi_enabled true $ERL"; fi
 
 if [ -z "$ERL_PATH" ]; then
   if [ -f "$SCRIPT_PATH/../releases/RELEASES" ] && [ -f "$SCRIPT_PATH/erl" ]; then

lib/elixir/lib/io/ansi.ex

@@ -34,7 +34,7 @@ defmodule IO.ANSI do
   This function simply reads the configuration value for
   `:ansi_enabled` in the `:elixir` application. The value is by
   default false unless Elixir can detect during startup that
-  `stdout` is a terminal.
+  both `stdout` and `stderr` are terminals.
   """
   @spec enabled? :: boolean
   def enabled? do