First try at working around Stripe's iDEAL idempotency issues

src/pretix/plugins/stripe/payment.py

@@ -406,6 +406,20 @@ class StripeMethod(BasePaymentProvider):
             })
             raise PaymentException(_('Stripe reported an error with your card: %s') % err['message'])
 
+        # This is not an error we normally expect, however some payment methods like iDEAL will redirect
+        # the user back to our confirmation page at the same time from two devices: the web browser the
+        # purchase is executed from and the online banking app the payment is authorized from.
+        # In this case we will just log the idempotency error but not expose it to the user and just
+        # forward them back to their order page. There is a good chance that by the time the user hits
+        # the order page, the other request has gone through and the payment is confirmed.
+        except stripe.error.IdempotencyError as e:
+            if e.json_body and 'error' in e.json_body:
+                err = e.json_body['error']
+                logger.exception('Stripe error: %s' % str(err))
+            else:
+                logger.exception('Stripe error: %s' % str(e))
+            return
+
         except stripe.error.StripeError as e:
             if e.json_body and 'error' in e.json_body:
                 err = e.json_body['error']