Remove extraneous test for already handled edge case

common/lib/xmodule/xmodule/util/date_utils.py

@@ -12,7 +12,7 @@ def get_default_time_display(dt, show_timezone=True):
     if dt is None:
         return ""
     timezone = ""
-    if dt is not None and show_timezone:
+    if show_timezone:
         if dt.tzinfo is not None:
             try:
                 timezone = " " + dt.tzinfo.tzname(dt)