Correctly process sqlalchemy_utils ChoiceType fields

flask_admin/form/fields.py

@@ -117,6 +117,13 @@ class Select2Field(fields.SelectField):
         self.allow_blank = allow_blank
         self.blank_text = blank_text or ' '
 
+        try:
+            from sqlalchemy_utils.types.choice import Choice
+        except ImportError:
+            class Choice(object):
+                pass
+        self.choice_cls = Choice
+
     def iter_choices(self):
         if self.allow_blank:
             yield (u'__None', self.blank_text, self.data is None)
@@ -129,7 +136,10 @@ class Select2Field(fields.SelectField):
             self.data = None
         else:
             try:
-                self.data = self.coerce(value)
+                if isinstance(value, self.choice_cls):
+                    self.data = self.coerce(value.code)
+                else:
+                    self.data = self.coerce(value)
             except (ValueError, TypeError):
                 self.data = None