Hi, 
I'm trying to insert data inside the mail_message_res_partner_rel table but I get an error:

code:
self.env['mail.message.res.partner.rel'].create({'message_id': 1,'partner_id': 1, })

mistake:

RPC_ERROR
Odoo Server Error
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/odoo/tools/safe_eval.py", line 362, in safe_eval
return unsafe_eval(c, globals_dict, locals_dict)
File "ir.actions.server(313,)", line 1, in
File "/mnt/extra-addons/xaxa/models/auto_install.py", line 118, in first_installation_bancali
self.env['mail.message.res.partner.rel'].create({
File "/usr/lib/python3/dist-packages/odoo/api.py", line 537, in __getitem__
return self.registry[model_name](self, (), ())
File "/usr/lib/python3/dist-packages/odoo/modules/registry.py", line 190, in __getitem__
return self.models[model_name]
KeyError: 'mail.message.res.partner.rel'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/odoo/http.py", line 1583, in _serve_db
return service_model.retrying(self._serve_ir_http, self.env)
File "/usr/lib/python3/dist-packages/odoo/service/model.py", line 134, in retrying
result = func()
File "/usr/lib/python3/dist-packages/odoo/http.py", line 1610, in _serve_ir_http
response = self.dispatcher.dispatch(rule.endpoint, args)
File "/usr/lib/python3/dist-packages/odoo/http.py", line 1807, in dispatch
result = self.request.registry['ir.http']._dispatch(endpoint)
File "/usr/lib/python3/dist-packages/odoo/addons/base/models/ir_http.py", line 154, in _dispatch
result = endpoint(**request.params)
File "/usr/lib/python3/dist-packages/odoo/http.py", line 696, in route_wrapper
result = endpoint(self, *args, **params_ok)
File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/dataset.py", line 46, in call_button
action = self._call_kw(model, method, args, kwargs)
File "/usr/lib/python3/dist-packages/odoo/addons/web/controllers/dataset.py", line 33, in _call_kw
return call_kw(request.env[model], method, args, kwargs)
File "/usr/lib/python3/dist-packages/odoo/api.py", line 461, in call_kw
result = _call_kw_multi(method, model, args, kwargs)
File "/usr/lib/python3/dist-packages/odoo/api.py", line 448, in _call_kw_multi
result = method(recs, *args, **kwargs)
File "/usr/lib/python3/dist-packages/odoo/addons/base/models/ir_cron.py", line 86, in method_direct_trigger
cron.with_user(cron.user_id).with_context({'lastcall': cron.lastcall}).ir_actions_server_id.run()
File "/usr/lib/python3/dist-packages/odoo/addons/base/models/ir_actions.py", line 668, in run
res = runner(run_self, eval_context=eval_context)
File "/usr/lib/python3/dist-packages/odoo/addons/base/models/ir_actions.py", line 538, in _run_action_code_multi
safe_eval(self.code.strip(), eval_context, mode="exec", nocopy=True, filename=str(self)) # nocopy allows to return 'action'
File "/usr/lib/python3/dist-packages/odoo/tools/safe_eval.py", line 376, in safe_eval
raise ValueError('%s: "%s" while evaluating\n%r' % (ustr(type(e)), ustr(e), expr))
ValueError: : "mail.message.res.partner.rel" while evaluating
'model.first_installation_bancali()'

The above server error caused the following client error:
RPC_ERROR: Odoo Server Error
at makeErrorFromResponse (http://localhost:8069/web/assets/debug/web.assets_backend.js:10216:19)
at XMLHttpRequest. (http://localhost:8069/web/assets/debug/web.assets_backend.js:10269:27)