Add a minimal length for voucher codes

src/pretix/base/models/vouchers.py

@@ -2,6 +2,7 @@ from decimal import Decimal
 
 from django.conf import settings
 from django.core.exceptions import ValidationError
+from django.core.validators import MinLengthValidator
 from django.db import models
 from django.utils.crypto import get_random_string
 from django.utils.timezone import now
@@ -92,6 +93,7 @@ class Voucher(LoggedModel):
         verbose_name=_("Voucher code"),
         max_length=255, default=generate_code,
         db_index=True,
+        validators=[MinLengthValidator(5)]
     )
     max_usages = models.PositiveIntegerField(
         verbose_name=_("Maximum usages"),

src/tests/control/test_vouchers.py

@@ -205,6 +205,12 @@ class VoucherFormTest(SoupTest):
         v = Voucher.objects.latest('pk')
         assert v.block_quota
 
+    def test_create_short_code(self):
+        self._create_voucher({
+            'itemvar': '%d-%d' % (self.shirt.pk, self.shirt_red.pk),
+            'code': 'ABC'
+        }, expected_failure=True)
+
     def test_create_blocking_variation_voucher_quota_full(self):
         self.quota_shirts.size = 0
         self.quota_shirts.save()