diff --git a/data/model/legacy.py b/data/model/legacy.py
index 94386cb53..5c632fbad 100644
--- a/data/model/legacy.py
+++ b/data/model/legacy.py
@@ -2778,11 +2778,19 @@ def cancel_repository_build(build, work_queue):
     return True
 
 def _get_repository_events(repository, time_delta, time_delta_earlier, clause):
+  """ Returns a pair representing the count of the number of events for the given
+      repository in each of the specified time deltas. The date ranges are calculated by
+      taking the current time today and subtracting the time delta given. Since
+      we want to grab *two* ranges, we restrict the second range to be greater
+      than the first (i.e. referring to an earlier time), so we can conduct the
+      lookup in a single query. The clause is used to further filter the kind of
+      events being found.
+  """
   since = date.today() - time_delta
   since_earlier = date.today() - time_delta_earlier
 
   if since_earlier >= since:
-    raise Exception('time_delta_earlier must be greater than time_delta')
+    raise ValueError('time_delta_earlier must be greater than time_delta')
 
   # This uses a CASE WHEN inner clause to further filter the count.
   formatted = since.strftime('%Y-%m-%d')
@@ -2799,22 +2807,22 @@ def _get_repository_events(repository, time_delta, time_delta_earlier, clause):
 
 
 def get_repository_pushes(repository, time_delta, time_delta_earlier):
-  push_repo = LogEntryKind.get(name = 'push_repo')
+  push_repo = LogEntryKind.get(name='push_repo')
   clauses = (LogEntry.kind == push_repo)
   return _get_repository_events(repository, time_delta, time_delta_earlier, clauses)
 
 
 def get_repository_pulls(repository, time_delta, time_delta_earlier):
-  repo_pull = LogEntryKind.get(name = 'pull_repo')
-  repo_verb = LogEntryKind.get(name = 'repo_verb')
+  repo_pull = LogEntryKind.get(name='pull_repo')
+  repo_verb = LogEntryKind.get(name='repo_verb')
   clauses = ((LogEntry.kind == repo_pull) | (LogEntry.kind == repo_verb))
   return _get_repository_events(repository, time_delta, time_delta_earlier, clauses)
 
 
 def get_repository_usage():
   one_month_ago = date.today() - timedelta(weeks=4)
-  repo_pull = LogEntryKind.get(name = 'pull_repo')
-  repo_verb = LogEntryKind.get(name = 'repo_verb')
+  repo_pull = LogEntryKind.get(name='pull_repo')
+  repo_verb = LogEntryKind.get(name='repo_verb')
   return (LogEntry.select(LogEntry.ip, LogEntry.repository)
                   .where((LogEntry.kind == repo_pull) | (LogEntry.kind == repo_verb))
                   .where(~(LogEntry.repository >> None))