cooperative-market/beesdoo_account/models/account_invoice.py

from odoo import api, fields, models, _
from odoo.exceptions import UserError


class AccountInvoice(models.Model):
    _inherit = "account.invoice"

    @api.multi
    def action_invoice_open(self):
        if self.user_has_groups(
                'beesdoo_account.'
                'group_validate_invoice_negative_total_amount'):
            return self.action_invoice_negative_amount_open()
        return super(AccountInvoice, self).action_invoice_open()

    @api.multi
    def action_invoice_negative_amount_open(self):
        """Identical to action_invoice_open without UserError on an invoice with a negative total amount"""
        to_open_invoices = self.filtered(lambda inv: inv.state != 'open')
        if to_open_invoices.filtered(lambda inv: not inv.partner_id):
            raise UserError(_("The field Vendor is required, please complete it to validate the Vendor Bill."))
        if to_open_invoices.filtered(lambda inv: inv.state != 'draft'):
            raise UserError(_("Invoice must be in draft state in order to validate it."))
        if to_open_invoices.filtered(lambda inv: not inv.account_id):
            raise UserError(
                _('No account was found to create the invoice, be sure you have installed a chart of account.'))
        to_open_invoices.action_date_assign()
        to_open_invoices.action_move_create()
        return to_open_invoices.invoice_validate()