diff --git a/jupyterhub/jupyterhub/handlers/base.py b/jupyterhub/jupyterhub/handlers/base.py
index 75d38d00..d6d1c5d9 100644
--- a/jupyterhub/jupyterhub/handlers/base.py
+++ b/jupyterhub/jupyterhub/handlers/base.py
@@ -1527,14 +1527,10 @@ class UserUrlHandler(BaseHandler):
 
         # if request is expecting JSON, assume it's an API request and fail with 503
         # because it won't like the redirect to the pending page
-        if (
-            get_accepted_mimetype(
-                self.request.headers.get('Accept', ''),
-                choices=['application/json', 'text/html'],
-            )
-            == 'application/json'
-            or 'api' in user_path.split('/')
-        ):
+        if get_accepted_mimetype(
+            self.request.headers.get('Accept', ''),
+            choices=['application/json', 'text/html'],
+        ) == 'application/json' or 'api' in user_path.split('/'):
             self._fail_api_request(user_name, server_name)
             return
 
@@ -1616,7 +1612,7 @@ class UserUrlHandler(BaseHandler):
         if redirects:
             self.log.warning("Redirect loop detected on %s", self.request.uri)
             # add capped exponential backoff where cap is 10s
-            await asyncio.sleep(min(1 * (2 ** redirects), 10))
+            await asyncio.sleep(min(1 * (2**redirects), 10))
             # rewrite target url with new `redirects` query value
             url_parts = urlparse(target)
             query_parts = parse_qs(url_parts.query)
diff --git a/jupyterhub/jupyterhub/singleuser/mixins.py b/jupyterhub/jupyterhub/singleuser/mixins.py
index 0b3b2207..706375ae 100755
--- a/jupyterhub/jupyterhub/singleuser/mixins.py
+++ b/jupyterhub/jupyterhub/singleuser/mixins.py
@@ -492,7 +492,7 @@ class SingleUserNotebookAppMixin(Configurable):
                     i,
                     RETRIES,
                 )
-                await asyncio.sleep(min(2 ** i, 16))
+                await asyncio.sleep(min(2**i, 16))
             else:
                 break
         else:
diff --git a/jupyterhub/tests/test_api.py b/jupyterhub/tests/test_api.py
index 968fea70..c0a8bcf9 100644
--- a/jupyterhub/tests/test_api.py
+++ b/jupyterhub/tests/test_api.py
@@ -1873,7 +1873,8 @@ async def test_auth_managed_groups(request, app, group, user):
         data=json.dumps({"users": [user.name]}),
     )
     assert r.status_code == 400
-    
+
+
 @mark.group
 async def test_group_add_properties(app):
     db = app.db
@@ -1899,6 +1900,7 @@ async def test_group_add_properties(app):
         properties_object[k] for k in properties_object
     )
 
+
 # -----------------
 # Service API tests
 # -----------------