Used modern idiom in collectstatic command.

Replaced set(<generator expression>) with set comprehension.

django/contrib/staticfiles/management/commands/collectstatic.py

@@ -79,7 +79,7 @@ class Command(BaseCommand):
         ignore_patterns = options['ignore_patterns']
         if options['use_default_ignore_patterns']:
             ignore_patterns += apps.get_app_config('staticfiles').ignore_patterns
-        self.ignore_patterns = list(set(os.path.normpath(p) for p in ignore_patterns))
+        self.ignore_patterns = list({os.path.normpath(p) for p in ignore_patterns})
         self.post_process = options['post_process']
 
     def collect(self):