Remove unused attribute

Library/Homebrew/exceptions.rb

@@ -154,12 +154,11 @@ class FormulaConflictError < Homebrew::InstallationError
 end
 
 class BuildError < Homebrew::InstallationError
-  attr_reader :exit_status, :command, :env
+  attr_reader :command, :env
 
-  def initialize formula, cmd, args, es
+  def initialize formula, cmd, args
     @command = cmd
     @env = ENV.to_hash
-    @exit_status = es.exitstatus rescue 1
     args = args.map{ |arg| arg.to_s.gsub " ", "\\ " }.join(" ")
     super formula, "Failed executing: #{command} #{args}"
   end

Library/Homebrew/formula.rb

@@ -573,7 +573,7 @@ class Formula
         f.puts
         require 'cmd/config'
         Homebrew.write_build_config(f)
-        raise BuildError.new(self, cmd, args, $?)
+        raise BuildError.new(self, cmd, args)
       end
     end
   ensure