diff --git a/CHANGELOG b/CHANGELOG
index b3a708f15..c3c13f20d 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -8,6 +8,8 @@ Version 2.0.0 (unreleased)
 ==========================
 
 - Changed supported Python version to >= 3.3
+- Used Django 1.7 as lowest requirement
+- Refactoring of the participant app. Now called 'users'
 
 Version 1.6.1 (unreleased)
 ==========================
diff --git a/openslides/assignment/models.py b/openslides/assignment/models.py
index 7e85602ee..460c86780 100644
--- a/openslides/assignment/models.py
+++ b/openslides/assignment/models.py
@@ -296,7 +296,7 @@ class AssignmentPoll(SlideMixin, RelatedModelMixin, CollectDefaultVotesMixin,
 
     option_class = AssignmentOption
     assignment = models.ForeignKey(Assignment, related_name='poll_set')
-    yesnoabstain = models.BooleanField()
+    yesnoabstain = models.BooleanField(default=False)
     description = models.CharField(
         max_length=79, null=True, blank=True,
         verbose_name=ugettext_lazy("Comment on the ballot paper"))
diff --git a/openslides/core/models.py b/openslides/core/models.py
index 82c1d6668..86b5a4783 100644
--- a/openslides/core/models.py
+++ b/openslides/core/models.py
@@ -1,13 +1,15 @@
 from django.core.urlresolvers import reverse
 from django.db import models
 from django.utils.translation import ugettext_lazy, ugettext_noop
-from django.contrib.auth import get_user_model
+# TODO: activate the following line after using the apploader
+# from django.contrib.auth import get_user_model
 
 from openslides.utils.models import AbsoluteUrlMixin
 from openslides.projector.models import SlideMixin
 
 # Imports the default user so that other apps can import it from here.
-User = get_user_model()
+# TODO: activate this with the new apploader
+# User = get_user_model()
 
 
 class CustomSlide(SlideMixin, AbsoluteUrlMixin, models.Model):
diff --git a/openslides/users/forms.py b/openslides/users/forms.py
index 8a5d0bddf..ddecb6d71 100644
--- a/openslides/users/forms.py
+++ b/openslides/users/forms.py
@@ -1,8 +1,7 @@
 from django import forms
 from django.conf import settings
 from django.contrib.auth.models import Permission
-from django.utils.translation import ugettext as _
-from django.utils.translation import ugettext_lazy
+from django.utils.translation import ugettext as _, ugettext_lazy
 
 from openslides.config.api import config
 from openslides.utils.forms import (CssClassMixin,
@@ -58,7 +57,7 @@ class UserUpdateForm(UserCreateForm):
 
     def __init__(self, *args, **kwargs):
         self.request = kwargs.pop('request')
-        return super(UserUpdateForm, self).__init__(*args, **kwargs)
+        return super().__init__(*args, **kwargs)
 
     def clean(self, *args, **kwargs):
         """
@@ -74,7 +73,7 @@ class UserUpdateForm(UserCreateForm):
         return super().clean(*args, **kwargs)
 
 
-class GroupForm(forms.ModelForm, CssClassMixin):
+class GroupForm(CssClassMixin, forms.ModelForm):
     permissions = LocalizedModelMultipleChoiceField(
         queryset=Permission.objects.all(), label=ugettext_lazy('Permissions'),
         required=False)
@@ -83,6 +82,7 @@ class GroupForm(forms.ModelForm, CssClassMixin):
 
     class Meta:
         model = Group
+        fields = '__all__'
 
     def __init__(self, *args, **kwargs):
         # Take request argument
diff --git a/openslides/utils/tornado_webserver.py b/openslides/utils/tornado_webserver.py
index 2df4a1b82..d8c2c52b8 100644
--- a/openslides/utils/tornado_webserver.py
+++ b/openslides/utils/tornado_webserver.py
@@ -3,8 +3,7 @@ import posixpath
 from urllib.parse import unquote
 
 from django.conf import settings
-from django.core.handlers.wsgi import WSGIHandler as Django_WSGIHandler
-from django.utils.translation import ugettext as _
+from django.core.wsgi import get_wsgi_application
 from sockjs.tornado import SockJSRouter, SockJSConnection
 from tornado.httpserver import HTTPServer
 from tornado.ioloop import IOLoop
@@ -72,14 +71,14 @@ def run_tornado(addr, port):
 
     # Print listening address and port to command line
     if addr == '0.0.0.0':
-        url_string = _("the machine's local ip address")
+        url_string = "the machine's local ip address"
     else:
         url_string = 'http://%s:%s' % (addr, port)
     # TODO: don't use print, use django logging
-    print(_("Starting OpenSlides' tornado webserver listening to %(url_string)s") % {'url_string': url_string})
+    print("Starting OpenSlides' tornado webserver listening to %(url_string)s" % {'url_string': url_string})
 
     # Setup WSGIContainer
-    app = WSGIContainer(Django_WSGIHandler())
+    app = WSGIContainer(get_wsgi_application())
 
     # Collect urls
     projectpr_socket_js_router = SockJSRouter(ProjectorSocketHandler, '/projector/socket')
diff --git a/openslides/utils/views.py b/openslides/utils/views.py
index d46922ad4..13a953cc4 100644
--- a/openslides/utils/views.py
+++ b/openslides/utils/views.py
@@ -9,8 +9,7 @@ from django.core.exceptions import ImproperlyConfigured, PermissionDenied
 from django.core.urlresolvers import reverse
 from django.http import (HttpResponse, HttpResponseRedirect)
 from django.utils.decorators import method_decorator
-from django.utils.translation import ugettext as _
-from django.utils.translation import ugettext_lazy
+from django.utils.translation import ugettext as _, ugettext_lazy
 from django.views import generic as django_views
 from django.views.generic.detail import SingleObjectMixin
 from reportlab.lib.units import cm
@@ -534,7 +533,7 @@ class PDFView(PermissionMixin, View):
     View to generate an PDF.
     """
 
-    filename = _('undefined-filename')
+    filename = ugettext_lazy('undefined-filename')
     top_space = 3
     document_title = None
 
diff --git a/requirements_production.txt b/requirements_production.txt
index f373f58ba..10962bda7 100644
--- a/requirements_production.txt
+++ b/requirements_production.txt
@@ -1,5 +1,5 @@
 # Requirements for OpenSlides in production in alphabetical order
-Django>=1.6,<1.7
+Django>=1.7,<1.8
 beautifulsoup4>=4.1,<4.4
 bleach>=1.4,<1.5
 django-ckeditor-updated>=4.2.3,<4.3
diff --git a/tests/mediafile/tests.py b/tests/mediafile/tests.py
index ae0239da2..0228f2701 100644
--- a/tests/mediafile/tests.py
+++ b/tests/mediafile/tests.py
@@ -8,7 +8,7 @@ from django.core.files.uploadedfile import SimpleUploadedFile
 from django.test.client import Client
 
 from openslides.mediafile.models import Mediafile
-from openslides.core.models import User
+from openslides.users.models import User
 from openslides.utils.test import TestCase