Use server.env.techname.mixin

server_environment_delivery/models/delivery_carrier.py

@@ -5,7 +5,7 @@ from odoo import models
 
 class DeliveryCarrier(models.Model):
     _name = "delivery.carrier"
-    _inherit = ["delivery.carrier", "server.env.mixin"]
+    _inherit = ["delivery.carrier", "server.env.techname.mixin", "server.env.mixin"]
 
     @property
     def _server_env_fields(self):

setup/server_environment_delivery/odoo/addons/server_environment_delivery

@@ -0,0 +1 @@
+../../../../server_environment_delivery

setup/server_environment_delivery/setup.py

@@ -0,0 +1,6 @@
+import setuptools
+
+setuptools.setup(
+    setup_requires=['setuptools-odoo'],
+    odoo_addon=True,
+)