diff --git a/modoboa/extensions/radicale/__init__.py b/modoboa/extensions/radicale/__init__.py
index 5e28f04a5..d7d884cf3 100644
--- a/modoboa/extensions/radicale/__init__.py
+++ b/modoboa/extensions/radicale/__init__.py
@@ -3,9 +3,11 @@ Radicale management frontend.
 
 """
 import sys
+
 from django.contrib.auth.models import Permission, Group
 from django.contrib.contenttypes.models import ContentType
 from django.utils.translation import ugettext_lazy
+
 from modoboa.lib import events, parameters
 from modoboa.lib.permissions import add_permissions_to_group
 from modoboa.core.extensions import ModoExtension, exts_pool
@@ -28,14 +30,16 @@ def init_limits_dependant_features():
 
 
 class Radicale(ModoExtension):
-    """
-    """
+
+    """Radicale extension declaration."""
+
     name = "radicale"
     label = ugettext_lazy("Radicale management")
     version = "1.0"
     url = "calendars"
     description = ugettext_lazy(
-        "Management frontend for Radicale, a simple calendar and contact server."
+        "Management frontend for Radicale, a simple calendar and contact "
+        "server."
     )
 
     def init(self):
diff --git a/modoboa/extensions/radicale/forms.py b/modoboa/extensions/radicale/forms.py
index 857cfbc2c..14472ded1 100644
--- a/modoboa/extensions/radicale/forms.py
+++ b/modoboa/extensions/radicale/forms.py
@@ -1,13 +1,15 @@
 """
 Radicale extension forms.
 """
+
 from django import forms
 from django.core.urlresolvers import reverse
 from django.utils.translation import ugettext as _, ugettext_lazy
-from modoboa.lib.web_utils import render_to_json_response
-from modoboa.lib.form_utils import WizardForm, TabForms, DynamicForm
+
 from modoboa.extensions.admin.models import Domain, Mailbox
 from modoboa.extensions.radicale.models import UserCalendar, SharedCalendar
+from modoboa.lib.form_utils import WizardForm, TabForms, DynamicForm
+from modoboa.lib.web_utils import render_to_json_response
 
 
 class UserCalendarForm(forms.ModelForm):
@@ -122,7 +124,7 @@ class RightsForm(forms.Form, DynamicForm):
             pos = int(res.group(1)) if res else None
             usernames[value] = pos
         for rule in self.calendar.rules.select_related().all():
-            if not rule.mailbox.full_address in usernames:
+            if rule.mailbox.full_address not in usernames:
                 rule.delete()
         for username, pos in usernames.iteritems():
             local_part, domname = split_mailbox(username)
diff --git a/modoboa/extensions/radicale/templatetags/radicale_tags.py b/modoboa/extensions/radicale/templatetags/radicale_tags.py
index ab28d44fd..83bc07994 100644
--- a/modoboa/extensions/radicale/templatetags/radicale_tags.py
+++ b/modoboa/extensions/radicale/templatetags/radicale_tags.py
@@ -2,15 +2,17 @@
 Custom template tags.
 """
 from django import template
-from django.template.loader import render_to_string
 from django.core.urlresolvers import reverse
+from django.template.loader import render_to_string
 from django.utils.translation import ugettext as _
-from modoboa.lib.web_utils import render_actions
+
 from modoboa.lib.templatetags.lib_tags import render_link
+from modoboa.lib.web_utils import render_actions
 
 
 register = template.Library()
 
+
 @register.simple_tag
 def radicale_left_menu(user):
     """Menu located inside the left column.
@@ -96,7 +98,7 @@ def render_rule_fields(form):
     result = ""
     while True:
         fname = "username_%d" % cpt
-        if not fname in form.fields:
+        if fname not in form.fields:
             break
         rfieldname = "read_access_%d" % cpt
         wfieldname = "write_access_%d" % cpt