Bug 1354012 - Fixed nice_type_name function always returning basestring. r=gfritzsche

Changed isinstance function to issubclass function since the nice_type_name function takes a type object as its input

toolkit/components/telemetry/parse_events.py

@@ -20,7 +20,7 @@ DATE_PATTERN = r'^[0-9]{4}-[0-9]{2}-[0-9]{2}$'
 
 
 def nice_type_name(t):
-    if isinstance(t, basestring):
+    if issubclass(t, basestring):
         return "string"
     return t.__name__