[PYLINT-FLAKE8][addons-vauxoo] Pylint and Flake8 actions over some modules done for version 7

Pylint and Flake8 was a applied to this modules, that are being used by some modules in the oml:

- account_voucher_tax
- hr_expense_replenishment
- hr_expense_replenishment_tax
- invoice_datetime
@jorgenaranjo 
La pep8 no menciona nada al respecto, y se cumple con lo requerido.
Entonces, las vamos a dejar así