KeyError when upgrading custom model in odoo 12

Question

When I Install a custom model(apps) in odoo 12 There are no errors and I can use this model. But when I change for example a field width in the formview I receive an KeyError like: File "C:\Bitnami\odoo-12\apps\odoo\Lib\site-packages\odoo-12.0.post20200815-py3.7.egg\odoo\modules\registry.py", line 177, in getitem return self.models [model_name] KeyError : 'qualities'

Whatever I change in formview, I'll still get the same error. PY-source

from odoo import models, fields, api, _
from odoo.tools import ustr
import math
#------------------------------------------------------------------------------
# Setup test module-1 
# Skip _name = when inherit product_template                                  -
#------------------------------------------------------------------------------
class Calc(models.Model):
    _name = 'calc'
    _description = 'Module t.b.v. calculation-functions

    qualities_id = fields.Many2one(comodel_name="qualities", string="Karton kwaliteit")
    qualities_dikte = fields.Float(string="Golf dikte", related='qualities_id.golfdikte', readonly=True)
    qualities_ref = fields.Char(string="Reference", related='qualities_id.reference', readonly=True)
    
XML-source (part)
<div>
  <field name="qualities_id"    class="oe_inline" />
  <field name="qualities_dikte" class="oe_inline" />
  <field name="qualities_ref"   class="oe_inline" />
</div>```

What can be the problem. Any advice would be welcome.
Thanks in advanced.

Answer 1

Problem at this line:

qualities_id = fields.Many2one(comodel_name="qualities", string="Karton kwaliteit")

When we declare any field with Many2one datatype, Odoo looks for the destination database table. In your case, table names are qualities.

Following way we can resolve it:

• If the qualities table doesn't exist, Change data type if you don't have any qualities table.
• If a qualities table exists, Check.py import file sequence or make sure qualities code executes before you use it in any other file or same file.