Use global var $stderr instead of constant STDERR

developer/bin/generate_cask_token

@@ -384,9 +384,9 @@ def report
   puts "Proposed file name:           #{cask_file_name}"
   puts "Cask Header Line:             cask '#{cask_token}' do"
   if warnings.length > 0
-    STDERR.puts "\n"
-    STDERR.puts warnings
-    STDERR.puts "\n"
+    $stderr.puts "\n"
+    $stderr.puts warnings
+    $stderr.puts "\n"
     exit 1
   end
 end

lib/hbc/system_command.rb

@@ -93,7 +93,7 @@ class Hbc::SystemCommand::Result
     external = File.basename(command.first)
     lines = garbage.strip.split("\n")
     opoo "Non-XML stdout from #{external}:"
-    STDERR.puts lines.map {|l| "    #{l}"}
+    $stderr.puts lines.map {|l| "    #{l}"}
   end
 
   def self._parse_plist(command, output)