Print string formatted ApiError on error

Make sure the user actually sees the error message in the UI

Related: SYS#5736

models/shipcloud_delivery_carrier.py

@@ -202,7 +202,7 @@ class SCDeliveryCarrier(models.Model):
         try:
             result = api.get_shipment_quote(shp)
         except shipcloud.ApiError as err:
-            raise Warning(err)
+            raise Warning(str(err))
         # { "shipment_quote": { "price": 42.12 } }
         return result['shipment_quote']['price']
 
@@ -242,7 +242,7 @@ class SCDeliveryCarrier(models.Model):
             result = api.create_shipment(shp, gen_label=True)
             #print("RES: %s" % result)
         except shipcloud.ApiError as err:
-            raise Warning(err)
+            raise Warning(str(err))
 
         # result = ["id", "carrier_tracking_no", "tracking_url", "label_url", "price"]
         # {u'label_url': u'https://shipping-labels.shipcloud.io/shipments/a948e8c2/e3fb26be59/label/shipping_label_e3fb26be59.pdf', u'price': 0.0, u'id': u'e3fb26be59a68acd04d565dda027efd415ca8117', u'tracking_url': u'https://track.shipcloud.io/e3fb26be59a68acd04d565dda027efd415ca8117', u'carrier_tracking_no': u'1ZV306W00493609016'}