[FIX] stock: error message for put in pack

closes odoo/odoo#140307

Signed-off-by: William Henrotin (whe) <whe@odoo.com>

addons/stock/i18n/stock.pot

@@ -5858,7 +5858,7 @@ msgstr ""
 #. odoo-python
 #: code:addons/stock/models/stock_picking.py:0
 #, python-format
-msgid "Please add 'Done' quantities to the picking to create a new pack."
+msgid "There is nothing eligible to put in a pack. Either there are no quantities to put in a pack or all products are already in a pack."
 msgstr ""
 
 #. module: stock

addons/stock/models/stock_picking.py

@@ -1500,7 +1500,7 @@ class Picking(models.Model):
                     self.action_assign()
                     return self._post_put_in_pack_hook(package)
                 return res
-            raise UserError(_("Please add 'Done' quantities to the picking to create a new pack."))
+            raise UserError(_("There is nothing eligible to put in a pack. Either there are no quantities to put in a pack or all products are already in a pack."))
 
     def button_scrap(self):
         self.ensure_one()