Validation errors now use simpler wording for users instead of showing internal technical details. This makes it easier for people to understand what needs to be corrected when data does not meet a rule.

Task : https://www.odoo.com/web?#id=10741&view_type=form&model=project.task&menu_id=3942&action=327
Pad : https://pad.odoo.com/p/r.GVQ0wU6KSlFqZV1d

This update removes editor-specific notes and extra blank lines from Python files across Odoo, with a visible sample concentrated in Accounting. It does not change product behavior, but keeps the codebase cleaner and easier for developers to maintain.

See discussions at https://github.com/odoo/odoo/pull/4174

PR generated with

``` bash
grep -i -r -l -e '# \?vim:' --include="*.py" | xargs sed -i -e '/# \?vim:/d'
find . -name "*.py" -print | xargs sed -i ':1;/^\n*$/{$d;N;b1}'
```