Impacted versions:
12.0

Steps to reproduce:
I have made a customization to postpone the creation of pos order picking
and delegate the task to a job
some time i get the error below

Current behavior:
2020-06-18 17:49:24,588 1370 ERROR cafe9.rabeh.io odoo.addons.base.models.ir_cron: Call from cron POS Orders: Process Pending Orders for server action #610 failed in Job #24 
Traceback (most recent call last):
  File "/opt/rabeh/odoo/odoo/addons/base/models/ir_cron.py", line 102, in _callback
    self.env['ir.actions.server'].browse(server_action_id).run()
  File "/opt/rabeh/odoo/odoo/addons/base/models/ir_actions.py", line 569, in run
    res = func(action, eval_context=eval_context)
  File "/opt/rabeh/odoo/odoo/addons/base/models/ir_actions.py", line 445, in run_action_code_multi
    safe_eval(action.sudo().code.strip(), eval_context, mode="exec", nocopy=True)  # nocopy allows to return 'action'
  File "/opt/rabeh/odoo/odoo/tools/safe_eval.py", line 350, in safe_eval
    return unsafe_eval(c, globals_dict, locals_dict)
  File "", line 1, in <module>
  File "/opt/rabeh-12/rabeh_addons/pos_pending_session/models/pos_order.py", line 68, in pending_picking_creation
    po_order.create_picking()
  File "/opt/rabeh-12/rabeh_addons/pos_pending_session/models/pos_order.py", line 36, in create_picking
    res = super(PosOrder, orders).create_picking()
  File "/opt/rabeh/odoo/addons/point_of_sale/models/pos_order.py", line 841, in create_picking
    order._force_picking_done(order_picking)
  File "/opt/rabeh/odoo/addons/point_of_sale/models/pos_order.py", line 856, in _force_picking_done
    picking.action_done()
  File "/opt/rabeh/odoo/addons/stock/models/stock_picking.py", line 631, in action_done
    todo_moves._action_done()
  File "/opt/rabeh/odoo/addons/purchase_stock/models/stock.py", line 96, in _action_done
    res = super(StockMove, self)._action_done()
  File "/opt/rabeh/odoo/addons/stock_account/models/stock.py", line 389, in _action_done
    res = super(StockMove, self)._action_done()
  File "/opt/rabeh/odoo/addons/stock/models/stock_move.py", line 1137, in _action_done
    moves_todo.mapped('move_line_ids')._action_done()
  File "/opt/rabeh/odoo/addons/stock/models/stock_move_line.py", line 445, in _action_done
    Quant._update_available_quantity(ml.product_id, ml.location_dest_id, quantity, lot_id=ml.lot_id, package_id=ml.result_package_id, owner_id=ml.owner_id, in_date=in_date)
  File "/opt/rabeh/odoo/addons/stock/models/stock_quant.py", line 216, in _update_available_quantity
    self._cr.execute("SELECT 1 FROM stock_quant WHERE id = %s FOR UPDATE NOWAIT", [quant.id], log_exceptions=False)
  File "/opt/rabeh/odoo/odoo/sql_db.py", line 148, in wrapper
    return f(self, *args, **kwargs)
  File "/opt/rabeh/odoo/odoo/sql_db.py", line 225, in execute
    res = self._obj.execute(query, params)
psycopg2.errors.SerializationFailure: could not serialize access due to concurrent update

Expected behavior:
i think this line should generate could not obtain lock
i was just wondering when it could generate "could not serialize access due to concurrent update"