Make PyIntEnum freeze enums in Alembic revisions

CHANGES.rst

@@ -84,6 +84,8 @@ Internal Changes
 - Add ``registrations`` kwarg to the ``event.designer.print_badge_template``
   signal (:issue:`4297`, thanks :user:`giusedb`)
 - Add ``registration_form_edited`` signal (:issue:`4421`, thanks :user:`omegak`)
+- Make PyIntEnum freeze enums in Alembic revisions (:issue:`4425`, thanks
+  :user:`omegak`)
 
 
 ----

indico/core/db/sqlalchemy/custom/int_enum.py

@@ -66,13 +66,22 @@ def coerce_set_value(self, value):
 
     def alembic_render_type(self, autogen_context):
         autogen_context.imports.add('from indico.core.db.sqlalchemy import PyIntEnum')
-        autogen_context.imports.add('from {} import {}'.format(self.enum.__module__, self.enum.__name__))
+        name = '_{}'.format(self.enum.__name__)
+        members = '\n'.join(['\t{} = {}'.format(k, v.value) for k, v in self.enum.__members__.iteritems()])
+        enum = ("""
+# ### code auto-generated by PyIntEnum - please adjust
+from enum import Enum
+class {name}(int, Enum):
+{members}
+# ### end of PyIntEnum code - please adjust
+        """.format(name=name, members=members))
+        autogen_context.imports.add(enum)
         if self.exclude_values:
-            return '{}({}, exclude_values={{{}}})'.format(type(self).__name__, self.enum.__name__, ', '.join(
-                '{}.{}'.format(self.enum.__name__, x.name) for x in sorted(self.exclude_values)
+            return '{}({}, exclude_values={{{}}})'.format(type(self).__name__, name, ', '.join(
+                '{}.{}'.format(name, x.name) for x in sorted(self.exclude_values)
             ))
         else:
-            return '{}({})'.format(type(self).__name__, self.enum.__name__)
+            return '{}({})'.format(type(self).__name__, name)
 
     def marshmallow_get_field_kwargs(self):
         return {'enum': self.enum}