[FIX] sale_purchase: Access rights error

Fine tuning of https://github.com/odoo/odoo/commit/6236ed1a5b138c5165929aa3f5c1d1f4f6aa061c#diff-2f6cca7f38255368e4a54b0a19406aa4

Steps to reproduce the bug:

- Install Sales and Purchase modules
- Create a user U with access rights to Sales
- Try to open an existing SO or try create one with U

Bug:

An access right error was raised because the non stored field purchase_line_count must be computed

PS: the compute_sudo had no effect on field purchase_line_count because it's a non stored field.

opw:2056746

closes odoo/odoo#36247

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>

addons/sale_purchase/models/sale_order.py

@@ -71,12 +71,12 @@ class SaleOrderLine(models.Model):
     _inherit = 'sale.order.line'
 
     purchase_line_ids = fields.One2many('purchase.order.line', 'sale_line_id', string="Generated Purchase Lines", readonly=True, help="Purchase line generated by this Sales item on order confirmation, or when the quantity was increased.")
-    purchase_line_count = fields.Integer("Number of generated purchase items", compute='_compute_purchase_count', compute_sudo=True)
+    purchase_line_count = fields.Integer("Number of generated purchase items", compute='_compute_purchase_count')
 
     @api.multi
     @api.depends('purchase_line_ids')
     def _compute_purchase_count(self):
-        database_data = self.env['purchase.order.line'].read_group([('sale_line_id', 'in', self.ids)], ['sale_line_id'], ['sale_line_id'])
+        database_data = self.env['purchase.order.line'].sudo().read_group([('sale_line_id', 'in', self.ids)], ['sale_line_id'], ['sale_line_id'])
         mapped_data = dict([(db['sale_line_id'][0], db['sale_line_id_count']) for db in database_data])
         for line in self:
             line.purchase_line_count = mapped_data.get(line.id, 0)