Fixed TypeError on Python 3

setup.py

@@ -33,7 +33,7 @@ setup_params = dict(
 	namespace_packages=['svg'],
 	include_package_data = True,
 	install_requires=[
-		'cssutils>=0.9.6b3',
+		'cssutils>=0.9.8a3',
 		'lxml>=2.0',
 	] + dateutil_req,
 	license = "MIT",

svg/charts/plot.py

@@ -1,4 +1,7 @@
-#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+"plot.py"
+
 import sys
 from itertools import izip, count, chain
 from lxml import etree
@@ -173,6 +176,8 @@ class Plot(Graph):
 		# above is same as
 		#max_value = max(map(lambda set: max(set['data'][data_index]), self.data))
 		spec_max = getattr(self, 'max_%s_value' % axis)
+		# Python 3 doesn't allow comparing None to int, so use -∞
+		if spec_max is None: spec_max = float('-Inf')
 		max_value = max(max_value, spec_max)
 		return max_value