Fix Python 3 test error.

Author: jpivarski

tests/testspec.py

@@ -18,7 +18,10 @@
 import math
 import sys
 import unittest
-import urllib2
+try:
+    from urllib2 import urlopen
+except ImportError:
+    from urllib.request import urlopen
 
 from histogrammar import *
 import histogrammar.version
@@ -44,12 +47,12 @@ def compare(self, x, y, name):
     def runTest(self):
         sys.stdout.write("Downloading expected results, generated by specification {0}...\n".format(histogrammar.version.specification))
         try:
-            testdata = json.load(urllib2.urlopen("http://histogrammar.org/test/{0}/test-data.json".format(histogrammar.version.specification)))
+            testdata = json.load(urlopen("http://histogrammar.org/test/{0}/test-data.json".format(histogrammar.version.specification)))
         except Exception as err:
             sys.stdout.write("could not download http://histogrammar.org/test/{0}/test-data.json\nbecause of {1}: {2}\n".format(histogrammar.version.specification, err.__class__.__name__, str(err)))
             return
         try:
-            testresults = json.load(urllib2.urlopen("http://histogrammar.org/test/{0}/test-results.json".format(histogrammar.version.specification)))
+            testresults = json.load(urlopen("http://histogrammar.org/test/{0}/test-results.json".format(histogrammar.version.specification)))
         except Exception as err:
             sys.stdout.write("could not download http://histogrammar.org/test/{0}/test-results.jsonbecause of {1}: {2}\n\n".format(histogrammar.version.specification, err.__class__.__name__, str(err)))
             return