[IMP] all/saas~18.1: Make _name or _inherit mandatory

This is a request following the revert of the use of class names
(concerning the python inheritance and typing project)

closes #171

Community: odoo/odoo#189889
Enterprise: odoo/enterprise#75293
Related: odoo/upgrade#6901
Signed-off-by: Raphael Collet <[email protected]>

src/mail/0.0.0/pre-report-migration.py

@@ -22,7 +22,7 @@ def migrate(cr, version):
 
 
 class MailMessage(models.Model):
-    _inherit = ["mail.message"]
+    _inherit = "mail.message"
     _module = "mail"
 
     @model_cr