Upgrade to Django 2.1 (#710)

* Upgrade to Django 2.0

* more models

* i18n foo

* Update setup.py

* Fix Sentry exception PRETIXEU-JC

* Enforce slug uniqueness

* Import sorting

* Upgrade to Django 2.1

* Travis config

* Try to fix PostgreSQL failure

* Smaller test matrix

* staticfiles→static

* Include request in all authenticate() calls

src/pretix/base/services/invoices.py

@@ -171,7 +171,7 @@ def build_cancellation(invoice: Invoice):
 
 
 def generate_cancellation(invoice: Invoice, trigger_pdf=True):
-    cancellation = copy.copy(invoice)
+    cancellation = copy.deepcopy(invoice)
     cancellation.pk = None
     cancellation.invoice_no = None
     cancellation.prefix = None

src/pretix/base/services/orders.py

@@ -923,7 +923,7 @@ class OrderChangeManager:
             op.save()
 
         try:
-            ia = copy.copy(self.order.invoice_address)
+            ia = copy.deepcopy(self.order.invoice_address)
             ia.pk = None
             ia.order = split_order
             ia.save()
@@ -947,7 +947,7 @@ class OrderChangeManager:
             split_order.total += fee.value
 
         for fee in self.order.fees.exclude(fee_type=OrderFee.FEE_TYPE_PAYMENT):
-            new_fee = copy.copy(fee)
+            new_fee = copy.deepcopy(fee)
             new_fee.pk = None
             new_fee.order = split_order
             split_order.total += new_fee.value