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/forms/__init__.py

@@ -3,7 +3,6 @@ import logging
 import i18nfield.forms
 from django import forms
 from django.forms.models import ModelFormMetaclass
-from django.utils import six
 from django.utils.crypto import get_random_string
 from formtools.wizard.views import SessionWizardView
 from hierarkey.forms import HierarkeyForm
@@ -25,7 +24,7 @@ class BaseI18nModelForm(i18nfield.forms.BaseI18nModelForm):
         super().__init__(*args, **kwargs)
 
 
-class I18nModelForm(six.with_metaclass(ModelFormMetaclass, BaseI18nModelForm)):
+class I18nModelForm(BaseI18nModelForm, metaclass=ModelFormMetaclass):
     pass
 
 

src/pretix/base/forms/auth.py

@@ -3,9 +3,10 @@ from django.conf import settings
 from django.contrib.auth.password_validation import (
     password_validators_help_texts, validate_password,
 )
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 from pretix.base.models import User
+from pretix.helpers.dicts import move_to_end
 
 
 class LoginForm(forms.Form):
@@ -36,7 +37,7 @@ class LoginForm(forms.Form):
         if not settings.PRETIX_LONG_SESSIONS or backend.url:
             del self.fields['keep_logged_in']
         else:
-            self.fields.move_to_end('keep_logged_in')
+            move_to_end(self.fields, 'keep_logged_in')
 
     def clean(self):
         if all(k in self.cleaned_data for k, f in self.fields.items() if f.required):

src/pretix/base/forms/questions.py

@@ -18,7 +18,7 @@ from django.forms import Select
 from django.utils.html import escape
 from django.utils.safestring import mark_safe
 from django.utils.translation import (
-    get_language, pgettext_lazy, ugettext_lazy as _,
+    get_language, gettext_lazy as _, pgettext_lazy,
 )
 from django_countries import countries
 from django_countries.fields import Country, CountryField

src/pretix/base/forms/user.py

@@ -4,7 +4,7 @@ from django.contrib.auth.password_validation import (
     password_validators_help_texts, validate_password,
 )
 from django.db.models import Q
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 from pytz import common_timezones
 
 from pretix.base.models import User

src/pretix/base/forms/validators.py

@@ -2,7 +2,7 @@ import re
 
 from django.core.exceptions import ValidationError
 from django.core.validators import BaseValidator
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 from i18nfield.strings import LazyI18nString
 
 

src/pretix/base/forms/widgets.py

@@ -4,7 +4,7 @@ from django import forms
 from django.utils.formats import get_format
 from django.utils.functional import lazy
 from django.utils.timezone import now
-from django.utils.translation import ugettext_lazy as _
+from django.utils.translation import gettext_lazy as _
 
 
 class DatePickerWidget(forms.DateInput):