Archives (CREATE_MONTHLY_ARCHIVE = True) think all months are "None"
https://irclogs.getnikola.com/2015/

To reproduce locally: get https://github.com/getnikola/irclogs-site create any random files in `posts/*.rst`.
diff --git a/nikola/plugins/task/archive.py b/nikola/plugins/task/archive.py
index 74c28c245..40baf9e16 100644
--- a/nikola/plugins/task/archive.py
+++ b/nikola/plugins/task/archive.py
@@ -97,7 +97,7 @@ class Archive(Taxonomy):
         elif len(classification) == 1:
             return classification[0]
         elif len(classification) == 2:
-            nikola.utils.LocaleBorg().get_month_name(int(classification[1]), lang)
+            return nikola.utils.LocaleBorg().get_month_name(int(classification[1]), lang)
         else:
             # Fallback
             return '/'.join(classification)
['nikola/plugins/task/archive.py']