Fix handling of itertools.izip

In python 3, izip became zip in the global space.

beat/web/plotters/views.py

@@ -29,6 +29,7 @@ import os
 import itertools
 import base64
 import collections
+import six
 
 import logging
 logger = logging.getLogger(__name__)
@@ -122,7 +123,12 @@ def plot(request):
         report_experiments, report_legends = report._get_experiments_and_alias(alias_filter)
 
     experiments = collections.OrderedDict()
-    for xpid, analyzer, output in itertools.izip(
+    if six.PY2:
+        zip_ = itertools.izip
+    else:
+        zip_ = zip
+
+    for xpid, analyzer, output in zip_(
             report_experiments or use.getlist('experiment') or use.getlist('experiment[]'),
             itertools.cycle(use.getlist('analyzer') or use.getlist('analyzer[]')),
             itertools.cycle(use.getlist('output') or use.getlist('output[]')),