Removed Python 3.3 polyfill (we already dropped support)

src/pretix/base/plugins.py

@@ -1,7 +1,4 @@
-try:  # NOQA
-    from enum import Enum
-except ImportError:  # NOQA
-    from flufl.enum import Enum  # remove this dependency when support for python <=3.3 is dropped
+from enum import Enum
 
 from django.apps import apps
 

src/requirements.txt

@@ -1,5 +1,4 @@
 -r requirements/production.txt
--r requirements/py33.txt
 -r requirements/dev.txt
 -r requirements/testing.txt
 -r requirements/paypal.txt

src/requirements/py33.txt

@@ -1,3 +0,0 @@
-# Polyfill for Python <3.4
-# Remove this, when Python 3.3 support is dropped
-flufl.enum