Use a set, lose dedupe function, since we no longer need to support Py23

Note: Once we stop supporting Py26, we can just make L623 a set comprehension.

supervisor/options.py

@@ -622,7 +622,7 @@ class ServerOptions(Options):
                     result_handler, section))
             pool_event_names = [x.upper() for x in
                                 list_of_strings(get(section, 'events', ''))]
-            pool_event_names = dedupe(pool_event_names)
+            pool_event_names = set(pool_event_names)
             if not pool_event_names:
                 raise ValueError('[%s] section requires an "events" line' %
                                  section)
@@ -1920,12 +1920,6 @@ def split_namespec(namespec):
         group_name, process_name = namespec, namespec
     return group_name, process_name
 
-def dedupe(L):
-    D = {}
-    for thing in L:
-        D[thing] = 1
-    return D.keys()
-
 # exceptions
 
 class ProcessException(Exception):