Hallo, I'm implementing Odoo for a business where they need to register payment automatically, given these values:

• payment date = invoice date

• paid amount = invoice total amount

• payment type = bank

I tried with the following code, but it fails with an error 

ValueError: "" while evaluating action_register_payment() 

It's likely I'm missing something about creating the voucher, which is a part that actually I don't know.

Code

In the invoice view: added a button 

<button name="invoice_paid" states="open" string="Invoice paid" class="oe_highlight" groups="base.group_user" />

that calls a transition by its signal

<record id="open_to_paid" model="workflow.transition">
 <field name="act_from" ref="account.act_open"/>
 <field name="act_to" ref="account.act_paid"/>
 <field name="signal">invoice_paid</field>
 </record>

the action of the act_paid activity has been improved

<record id="account.act_paid" model="workflow.activity">
 <field name="action">action_register_payment()
 confirm_paid()</field>
 </record>

 and finally the action_register_payment():

def action_register_payment(self):
for inv in self:
 journal_pool = self.env['account.journal']
 journal_id = journal_pool.search([('company_id','=',inv.company_id.id), ('code','=','BNK2')])[0].id
 journal = journal_pool.browse(journal_id)
 account_id = journal.default_debit_account_id.id
 vals = {
 'currency_id': inv.currency_id.id,
 'partner_id': inv.partner_id.id,
 'amount': inv.amount_total,
 'reference': inv.name,
 'name': inv.number,
 'type': 'payment',
 'date': inv.date_invoice,
 'period_id': inv.period_id.id,
 'journal_id': journal_id,
 'account_id': account_id,
 'writeoff_amount': 0.0,
 'paid': True,
 'narration': 'Automatically set to paid'
 }
 id = voucher_pool.create(vals)
 voucher_id = voucher_pool.browse(id)
 voucher_id.signal_workflow('proforma_voucher')
 voucher_pool = self.env['account.voucher']