diff --git a/osmchadjango/changeset/tasks.py b/osmchadjango/changeset/tasks.py
index 9b6be598..c0e1a052 100644
--- a/osmchadjango/changeset/tasks.py
+++ b/osmchadjango/changeset/tasks.py
@@ -3,6 +3,7 @@
 from os.path import join
 from urllib.parse import quote
 import yaml
+
 try:
     from yaml import CLoader as Loader
 except ImportError:
@@ -24,24 +25,23 @@ def create_changeset(changeset_id):
 
     # remove suspicion_reasons
     ch_dict = ch.get_dict()
-    ch_dict.pop('suspicion_reasons')
+    ch_dict.pop("suspicion_reasons")
 
     # remove bbox field if it is not a valid geometry
-    if ch.bbox == 'GEOMETRYCOLLECTION EMPTY':
-        ch_dict.pop('bbox')
+    if ch.bbox == "GEOMETRYCOLLECTION EMPTY":
+        ch_dict.pop("bbox")
 
     # save changeset.
     changeset, created = Changeset.objects.update_or_create(
-        id=ch_dict['id'],
-        defaults=ch_dict
-        )
+        id=ch_dict["id"], defaults=ch_dict
+    )
 
     if ch.suspicion_reasons:
         for reason in ch.suspicion_reasons:
             reason, created = SuspicionReasons.objects.get_or_create(name=reason)
             reason.changesets.add(changeset)
 
-    print('{c[id]} created'.format(c=ch_dict))
+    print("{c[id]} created".format(c=ch_dict))
     return changeset
 
 
@@ -51,14 +51,16 @@ def get_filter_changeset_file(url, geojson_filter=settings.CHANGESETS_FILTER):
     """
     cl = ChangesetList(url, geojson_filter)
     for c in cl.changesets:
-        print('Creating changeset {}'.format(c['id']))
-        create_changeset(c['id'])
+        print("Creating changeset {}".format(c["id"]))
+        create_changeset(c["id"])
 
 
 def format_url(n):
     """Return the URL of a replication file."""
-    n = str(n)
-    return join(settings.OSM_PLANET_BASE_URL, '00%s' % n[0], n[1:4], '%s.osm.gz' % n[4:])
+    n = "{num:0{width}}".format(num=n, width=9)
+    return join(
+        settings.OSM_PLANET_BASE_URL, n[0:3], n[3:6], "%s.osm.gz" % n[6:]
+    )
 
 
 def import_replications(start, end):
@@ -68,18 +70,15 @@ def import_replications(start, end):
     Import(start=start, end=end).save()
     urls = [format_url(n) for n in range(start, end + 1)]
     for url in urls:
-        print('Importing {}'.format(url))
+        print("Importing {}".format(url))
         get_filter_changeset_file(url)
 
 
 def get_last_replication_id():
-    """Get the id of the last replication file available on Planet OSM.
-    """
-    state = requests.get(
-        '{}state.yaml'.format(settings.OSM_PLANET_BASE_URL)
-        ).content
+    """Get the id of the last replication file available on Planet OSM."""
+    state = requests.get("{}state.yaml".format(settings.OSM_PLANET_BASE_URL)).content
     state = yaml.load(state, Loader)
-    return state.get('sequence')
+    return state.get("sequence")
 
 
 def fetch_latest():
@@ -88,7 +87,7 @@ def fetch_latest():
     FIXME: define error in except line
     """
     try:
-        last_import = Import.objects.all().order_by('-end')[0].end
+        last_import = Import.objects.all().order_by("-end")[0].end
     except:
         last_import = None
 
@@ -98,7 +97,13 @@ def fetch_latest():
         start = last_import + 1
     else:
         start = sequence - 1000
-    print("Importing replications from %d to %d" % (start, sequence,))
+    print(
+        "Importing replications from %d to %d"
+        % (
+            start,
+            sequence,
+        )
+    )
     import_replications(start, sequence)
 
 
@@ -106,34 +111,37 @@ class ChangesetCommentAPI(object):
     """Class that allows us to publish comments in changesets on the
     OpenStreetMap website.
     """
+
     def __init__(self, user, changeset_id):
         self.changeset_id = changeset_id
         user_token = user.social_auth.all().first().access_token
         self.client = OAuth1Session(
             settings.SOCIAL_AUTH_OPENSTREETMAP_KEY,
             client_secret=settings.SOCIAL_AUTH_OPENSTREETMAP_SECRET,
-            resource_owner_key=user_token['oauth_token'],
-            resource_owner_secret=user_token['oauth_token_secret']
-            )
-        self.url = '{}/api/0.6/changeset/{}/comment/'.format(
-            settings.OSM_SERVER_URL,
-            changeset_id
-            )
+            resource_owner_key=user_token["oauth_token"],
+            resource_owner_secret=user_token["oauth_token_secret"],
+        )
+        self.url = "{}/api/0.6/changeset/{}/comment/".format(
+            settings.OSM_SERVER_URL, changeset_id
+        )
 
     def post_comment(self, message=None):
         """Post comment to changeset."""
         response = self.client.post(
-            self.url,
-            data='text={}'.format(quote(message)).encode("utf-8")
-            )
+            self.url, data="text={}".format(quote(message)).encode("utf-8")
+        )
         if response.status_code == 200:
             print(
-                'Comment in the changeset {} posted successfully.'.format(
+                "Comment in the changeset {} posted successfully.".format(
                     self.changeset_id
-                    )
                 )
-            return {'success': True}
+            )
+            return {"success": True}
         else:
-            print("""Some error occurred and it wasn't possible to post the
-                comment to the changeset {}.""".format(self.changeset_id))
-            return {'success': False}
+            print(
+                """Some error occurred and it wasn't possible to post the
+                comment to the changeset {}.""".format(
+                    self.changeset_id
+                )
+            )
+            return {"success": False}