'Return a L{FilePath} representing the home directory of the given
avatar.  Override this in a subclass.
@param avatarId: A user identifier returned from a credentials checker.
@type avatarId: C{str}
@rtype: L{FilePath}'

def getHomeDirectory(self, avatarId):

    raise NotImplementedError(('%r    did    not    override    getHomeDirectory' % (self.__class__,)))
