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

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
@moylop260 
A mi no se me hace una forma elegante de cortar las variables. No se tu que opines, veo varios casos similares a estos.