[FIX] Refund payment: Error occurred while validating the field(s) amount_currency
[IMP] use ternary if/else operator and replace <> by !=
[MERGE]
[IMP] PEP8
[FIX] account_voucher: Refund payment: Error occurred while validating the field(s) amount_currency
[FIX] account_voucher: Refund payment: Error occurred while validating the field(s) amount_currency