Upgrade to Django 3.0 and other dependencies (#1568)

* Upgrade Django to 3.0 and other dependencies to recent versions

* Fix otp version contsraint

* Remove six dependency

* Resolve some warnings

* Fix failing tests

* Update django-countries

* Resolve all RemovedInDjango31Warnings in test suite

* Run isort

* Fix import

* Update PostgreSQL version on travis

src/pretix/base/exporters/answers.py

@@ -5,7 +5,7 @@ from zipfile import ZipFile
 
 from django import forms
 from django.dispatch import receiver
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix.base.models import QuestionAnswer
 

src/pretix/base/exporters/dekodi.py

@@ -6,7 +6,7 @@ import dateutil
 from django import forms
 from django.core.serializers.json import DjangoJSONEncoder
 from django.dispatch import receiver
-from django.utils.translation import ugettext, ugettext_lazy
+from django.utils.translation import gettext, gettext_lazy
 
 from pretix.base.i18n import language
 from pretix.base.models import Invoice, OrderPayment
@@ -79,7 +79,7 @@ class DekodiNREIExporter(BaseExporter):
                     payments.append({
                         'PTID': '5',
                         'PTN': 'Lastschrift',
-                        'PTNo4': ugettext('Event ticket {event}-{code}').format(
+                        'PTNo4': gettext('Event ticket {event}-{code}').format(
                             event=self.event.slug.upper(),
                             code=invoice.order.code
                         ),
@@ -199,19 +199,19 @@ class DekodiNREIExporter(BaseExporter):
             [
                 ('date_from',
                  forms.DateField(
-                     label=ugettext_lazy('Start date'),
+                     label=gettext_lazy('Start date'),
                      widget=forms.DateInput(attrs={'class': 'datepickerfield'}),
                      required=False,
-                     help_text=ugettext_lazy('Only include invoices issued on or after this date. Note that the invoice date does '
-                                             'not always correspond to the order or payment date.')
+                     help_text=gettext_lazy('Only include invoices issued on or after this date. Note that the invoice date does '
+                                            'not always correspond to the order or payment date.')
                  )),
                 ('date_to',
                  forms.DateField(
-                     label=ugettext_lazy('End date'),
+                     label=gettext_lazy('End date'),
                      widget=forms.DateInput(attrs={'class': 'datepickerfield'}),
                      required=False,
-                     help_text=ugettext_lazy('Only include invoices issued on or before this date. Note that the invoice date '
-                                             'does not always correspond to the order or payment date.')
+                     help_text=gettext_lazy('Only include invoices issued on or before this date. Note that the invoice date '
+                                            'does not always correspond to the order or payment date.')
                  )),
             ]
         )

src/pretix/base/exporters/invoices.py

@@ -7,7 +7,7 @@ import dateutil.parser
 from django import forms
 from django.db.models import Exists, OuterRef, Q
 from django.dispatch import receiver
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix.base.models import OrderPayment
 

src/pretix/base/exporters/mail.py

@@ -2,7 +2,7 @@ from collections import OrderedDict
 
 from django import forms
 from django.dispatch import receiver
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix.base.models import OrderPosition
 

src/pretix/base/exporters/orderlist.py

@@ -8,7 +8,7 @@ from django.db.models import (
 )
 from django.dispatch import receiver
 from django.utils.formats import date_format
-from django.utils.translation import pgettext, ugettext as _, ugettext_lazy
+from django.utils.translation import gettext as _, gettext_lazy, pgettext
 
 from pretix.base.models import (
     InvoiceAddress, InvoiceLine, Order, OrderPosition, Question,
@@ -22,7 +22,7 @@ from ..signals import register_data_exporters
 
 class OrderListExporter(MultiSheetListExporter):
     identifier = 'orderlist'
-    verbose_name = ugettext_lazy('Order data')
+    verbose_name = gettext_lazy('Order data')
 
     @property
     def sheets(self):
@@ -414,7 +414,7 @@ class OrderListExporter(MultiSheetListExporter):
 
 class PaymentListExporter(ListExporter):
     identifier = 'paymentlist'
-    verbose_name = ugettext_lazy('Order payments and refunds')
+    verbose_name = gettext_lazy('Order payments and refunds')
 
     @property
     def additional_form_fields(self):
@@ -485,7 +485,7 @@ class PaymentListExporter(ListExporter):
 
 class QuotaListExporter(ListExporter):
     identifier = 'quotalist'
-    verbose_name = ugettext_lazy('Quota availabilities')
+    verbose_name = gettext_lazy('Quota availabilities')
 
     def iterate_list(self, form_data):
         headers = [
@@ -514,7 +514,7 @@ class QuotaListExporter(ListExporter):
 
 class InvoiceDataExporter(MultiSheetListExporter):
     identifier = 'invoicedata'
-    verbose_name = ugettext_lazy('Invoice data')
+    verbose_name = gettext_lazy('Invoice data')
 
     @property
     def sheets(self):