[FIX] account: statement line amount rounding

See comment in code.

opw-676924

addons/account/models/account_bank_statement.py

@@ -392,6 +392,20 @@ class AccountBankStatementLine(models.Model):
         if self.amount_currency != 0 and self.amount == 0:
             raise ValidationError(_('If "Amount Currency" is specified, then "Amount" must be as well.'))
 
+    @api.model
+    def create(self, vals):
+        line = super(AccountBankStatementLine, self).create(vals)
+        # The most awesome fix you will ever see is below.
+        # Explanation: during a 'create', the 'convert_to_cache' method is not called. Moreover, at
+        # that point 'journal_currency_id' is not yet known since it is a related field. It means
+        # that the 'amount' field will not be properly rounded. The line below triggers a write on
+        # the 'amount' field, which will trigger the 'convert_to_cache' method, and ultimately round
+        # the field correctly.
+        # This is obviously an awful workaround, but at the time of writing, the ORM does not
+        # provide a clean mechanism to fix the issue.
+        line.amount = line.amount
+        return line
+
     @api.multi
     def unlink(self):
         for line in self: