Create ShippingAddresses with empty strings instead of None

ShippingAddress fields don't allow setting None (null=False), so for
missing values we should set empty strings instead.

If my analysis is correct, this fixes #100. If it doesn't, it's still a
correct change.

README.rst

@@ -67,9 +67,11 @@ Changelog
 * Display original Paypal error message instead of generic error message. `#101`_
 * Bugfix: Hide form buttons as expected. `#94`_
 * Bugfix: Correct signature for call to ``get_shipping_methods``. `#99`_
+* Bugfix: Don't fail in countries without postcode. `#100`_
 
 .. _`#94`: https://github.com/django-oscar/django-oscar-paypal/pull/94
 .. _`#99`: https://github.com/django-oscar/django-oscar-paypal/issues/99
+.. _`#100`: https://github.com/django-oscar/django-oscar-paypal/issues/100
 .. _`#101`: https://github.com/django-oscar/django-oscar-paypal/pull/101
 .. _`#107`: https://github.com/django-oscar/django-oscar-paypal/pull/107
 

paypal/express/views.py

@@ -346,7 +346,7 @@ def get_shipping_address(self, basket):
             line2=self.txn.value('PAYMENTREQUEST_0_SHIPTOSTREET2', default=""),
             line4=self.txn.value('PAYMENTREQUEST_0_SHIPTOCITY', default=""),
             state=self.txn.value('PAYMENTREQUEST_0_SHIPTOSTATE', default=""),
-            postcode=self.txn.value('PAYMENTREQUEST_0_SHIPTOZIP'),
+            postcode=self.txn.value('PAYMENTREQUEST_0_SHIPTOZIP', default=""),
             country=Country.objects.get(iso_3166_1_a2=self.txn.value('PAYMENTREQUEST_0_SHIPTOCOUNTRYCODE'))
         )
 
@@ -415,11 +415,11 @@ def post(self, request, *args, **kwargs):
             country = Country()
 
         shipping_address = ShippingAddress(
-            line1=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOSTREET', None),
-            line2=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOSTREET2', None),
-            line4=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOCITY', None),
-            state=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOSTATE', None),
-            postcode=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOZIP', None),
+            line1=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOSTREET', ''),
+            line2=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOSTREET2', ''),
+            line4=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOCITY', ''),
+            state=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOSTATE', ''),
+            postcode=self.request.POST.get('PAYMENTREQUEST_0_SHIPTOZIP', ''),
             country=country
         )
         methods = Repository().get_shipping_methods(