Test both reverse operations to invalidate ratio and divisor

When the value has repeating decimal, the comparison may fail for one
comparison but we must consider as valid value.

issue8966
review265001002

payment_term.py

@@ -222,11 +222,10 @@ class PaymentTermLine(sequence_ordered(), ModelSQL, ModelView):
                     gettext('account_invoice'
                         '.msg_payment_term_invalid_ratio_divisor',
                         line=line.rec_name))
-            ratio = line.ratio
-            divisor = line.divisor
-            line.on_change_ratio()
-            line.on_change_divisor()
-            if (line.divisor != divisor) or (line.ratio != ratio):
+            if (line.ratio != round(
+                        1 / line.divisor, cls.ratio.digits[1])
+                    and line.divisor != round(
+                        1 / line.ratio, cls.divisor.digits[1])):
                 raise PaymentTermValidationError(
                     gettext('account_invoice'
                         '.msg_payment_term_invalid_ratio_divisor',