Be tolerant to missing mail archive list page

Avoid failure when mail archive page is not found or empty.
Also remove non-existing OPNFV mail list.

Change-Id: Id7554e313d94cca7062fa662f45b526d88f1bac3

etc/default_data.json

@@ -30063,7 +30063,6 @@
         "https://lists.opnfv.org/pipermail/fds-dev/",
         "https://lists.opnfv.org/pipermail/infra-wg/",
         "https://lists.opnfv.org/pipermail/mano-wg/",
-        "https://lists.opnfv.org/pipermail/odl-wg/",
         "https://lists.opnfv.org/pipermail/openstack-dev/",
         "https://lists.opnfv.org/pipermail/opnfv-enduser-advisory-group/",
         "https://lists.opnfv.org/pipermail/opnfv-project-leads/",

stackalytics/processor/mls.py

@@ -54,6 +54,10 @@ TRAILING_RECORD = ('From ishakhat at mirantis.com  Tue Sep 17 07:30:43 2013\n'
 
 def _get_mail_archive_links(uri):
     content = utils.read_uri(uri)
+    if not content:
+        LOG.warning('Mail archive list is not found at %s', uri)
+        return []
+
     links = set(re.findall(r'\shref\s*=\s*[\'"]([^\'"]*\.txt\.gz)', content,
                            flags=re.IGNORECASE))
     return [parse.urljoin(uri, link) for link in links]