Fixed unit test.

modoboa/admin/app_settings.py

@@ -64,7 +64,8 @@ class AdminParametersForm(param_forms.AdminParametersForm):
             "Absolute path of the directory where DKIM private keys will "
             "be stored. Make sure this directory belongs to root user "
             "and is not readable by the outside world."
-        )
+        ),
+        required=False
     )
 
     dkim_default_key_length = forms.ChoiceField(

modoboa/core/tests/test_views.py

@@ -159,6 +159,8 @@ class SettingsTestCase(ModoTestCase):
         "admin-domains_must_have_authorized_mx": False,
         "core-random_password_length": "8",
         "admin-create_alias_on_mbox_rename": False,
+        "admin-dkim_keys_storage_dir": "",
+        "admin-dkim_default_key_length": 1024
     }
 
     def test_get_settings(self):