[FIX] base_import : show meaningful error message on import fail

Issue :
When you try to import a big file it will display a blank error.

Steps to reproduce the error :
1-install inventory and e-commerce
2-go to products and import records
3-upload the file attached the ticket

Reason :
Before, there was a type included in the `reason` but now
it seems that the error has no type neither a message.

Fix:
I tried to just output a general error.

opw-3410954

closes odoo/odoo#128272

Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>