Add initial support for color output in the build system

lib/naclports/__main__.py

 # Copyright (c) 2013 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Tool for manipulating naclports packages in python.
 
 This tool can be used to for working with naclports packages.
 It can also be incorporated into other tools that need to
 work with packages (e.g. 'update_mirror.py' uses it to iterate
 through all packages and mirror them on Google Cloud Storage).
@@ skipping 257 matching lines @@
         p = naclports.package.CreateInstalledPackage(package_name, config)
       else:
         p = source_package.CreatePackage(package_name, config)
       DoCmd(p)
 
 
 def main(args):
   try:
     run_main(args)
   except KeyboardInterrupt:
-    sys.stderr.write('naclports: interrupted\n')
+    sys.stderr.write('naclports: %s\n' % util.Color('interrupted', 'red'))
     return 1
   except error.Error as e:
-    sys.stderr.write('naclports: %s\n' % e)
+    sys.stderr.write('naclports: %s\n' % util.Color(str(e), 'red'))
     return 1
 
   return 0
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))