display datasets on hover if multiple datasets

.flake8

 [flake8]
-ignore = E501, E503
+ignore = E501, W503

portal/views/secure/datafile.py

@@ -70,9 +70,15 @@ class DataFilesJSONListView(LoginRequiredMixin, JSONListView):
         rows = []
 
         for o in self.object_list:
-            ndatasets = 1
             datasets = [d.name for d in o.datasets.all()]
-            datasets = '%s datasets' % len(datasets) if len(datasets)>ndatasets else ','.join(datasets)
+            datasets_length = len(datasets)
+            datasets = ', '.join(datasets)
+            if 1 < datasets_length:
+                datasets = '<span title="{0}">{1} {2}</span>'.format(
+                    datasets,
+                    datasets_length,
+                    ugettext('DataSets')
+                )
 
             row = {
                 'id': o.id,