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/plugins/ticketoutputpdf/__init__.py

@@ -1,6 +1,6 @@
 from django.apps import AppConfig
 from django.utils.functional import cached_property
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix import __version__ as version
 

src/pretix/plugins/ticketoutputpdf/exporters.py

@@ -5,7 +5,7 @@ from django import forms
 from django.conf import settings
 from django.core.files.base import ContentFile
 from django.db.models.functions import Coalesce
-from django.utils.translation import ugettext as _, ugettext_lazy
+from django.utils.translation import gettext as _, gettext_lazy
 from jsonfallback.functions import JSONExtract
 from PyPDF2.merger import PdfFileMerger
 
@@ -19,7 +19,7 @@ from .ticketoutput import PdfTicketOutput
 
 class AllTicketsPDF(BaseExporter):
     name = "alltickets"
-    verbose_name = ugettext_lazy("All PDF tickets in one file")
+    verbose_name = gettext_lazy("All PDF tickets in one file")
     identifier = "pdfoutput_all_tickets"
 
     @property

src/pretix/plugins/ticketoutputpdf/forms.py

@@ -1,5 +1,5 @@
 from django import forms
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix.base.services import tickets
 

src/pretix/plugins/ticketoutputpdf/models.py

@@ -2,7 +2,7 @@ import string
 
 from django.db import models
 from django.utils.crypto import get_random_string
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix.base.models import LoggedModel
 

src/pretix/plugins/ticketoutputpdf/signals.py

@@ -4,7 +4,7 @@ import json
 from django.dispatch import receiver
 from django.urls import reverse
 from django.utils.html import escape
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix.base.channels import get_all_sales_channels
 from pretix.base.signals import (  # NOQA: legacy import

src/pretix/plugins/ticketoutputpdf/ticketoutput.py

@@ -9,7 +9,7 @@ from django.core.files.storage import default_storage
 from django.http import HttpRequest
 from django.template.loader import get_template
 from django.utils.functional import cached_property
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 from PyPDF2 import PdfFileMerger
 
 from pretix.base.i18n import language

src/pretix/plugins/ticketoutputpdf/views.py

@@ -12,7 +12,7 @@ from django.shortcuts import redirect
 from django.templatetags.static import static
 from django.urls import reverse
 from django.utils.functional import cached_property
-from django.utils.translation import gettext, ugettext_lazy as _
+from django.utils.translation import gettext, gettext_lazy as _
 from django.views import View
 from django.views.generic import CreateView, DeleteView, DetailView, ListView
 from reportlab.lib import pagesizes