When I get a syntax error, it shows the line with the error, and then a little '^' on the next line, showing where the error is. However, the location of the '^' is a little misleading, since it isn't in the right spot. For example (not sure if it will format correctly though):
elif self.left == None and self.right =! None:
                          ^
The symbol should be under the +! instead of under the 'and.' Also, this problem doesn't occur with the font Courier.