% symbol causes expception when parsing help text

[evidex]

Help fields containing a % symbol cause an exception when using the -h or --help flags to parse help text.

% is obviously a special symbol used by the parser for some reason, however there seems to be no documentation of this, or any other reserved symbols.

Exception text - http://pastebin.ubuntu.com/7250072/ Python 2.7.3 Argparse 1.1