What steps will reproduce the problem?
1. Create the following Dot file:
digraph {
    a -> b[label="hi", decorate];   
}
(The validity of this graph can be verified by running Dot on it.)

2. Run  pydot.dot_parser.graph_definition().parseFile('/path/to/file.dot')

PyDot complains, 'ParseException: Expected "}" (at char 24), (line:2, col:15).'

This issue appears to be caused by an erroneous assumption in the P_AttrList 
class that attributes always appear in name/value pairs. 

I'm using the latest release of PyDot on Scientific Linux with Python 2.5.1.

I have provided a patch to fix this problem; it merely prevents suppression of 
the '=' character in attribute lists and uses that in P_AttrList construction 
to determine which attributes have values and which do not.