[FIX] core: log unexpected validation exceptions

Before this patch, any exception raised by a constraint method that
were not of type `ValidationError` were hard to debug, because the
origin line was never logged.

Explicitly logging the error (with traceback) when we catch it
ensures proper contextual info, even in the absence of exception
chaining.

closes #28612

odoo/models.py

@@ -1079,6 +1079,7 @@ def _validate_fields(self, field_names):
                 except ValidationError, e:
                     raise
                 except Exception, e:
+                    _logger.exception('Exception while validating constraint')
                     raise ValidationError("%s\n\n%s" % (_("Error while validating constraint"), tools.ustr(e)))
 
     @api.model