ref: 6776b0afba6b4b3f8efd76a8425831b3d8a59a77
parent: 572a7469373a4e3073043001dc9e61289259316d
author: Simon Tatham <anakin@pobox.com>
date: Sat Jan 9 12:21:36 EST 2010
Oops. Uncomment the difficulty exceptions! (Also add another constraint in validate_params.) [originally from svn r8824]