diff --git a/tljh/installer.py b/tljh/installer.py
index b1f704e6..1f4214c0 100644
--- a/tljh/installer.py
+++ b/tljh/installer.py
@@ -261,7 +261,9 @@ def ensure_user_environment(user_requirements_txt_file):
     # version specification used for the hub env.
     #
     with open(os.path.join(HERE, "requirements-hub-env.txt")) as f:
-        jupyterhub_version_spec = [line for line in f if line.startswith("jupyterhub>=")][0]
+        jupyterhub_version_spec = [
+            line for line in f if line.startswith("jupyterhub>=")
+        ][0]
     conda.ensure_pip_packages(USER_ENV_PREFIX, [jupyterhub_version_spec], upgrade=True)
 
     # Install user environment extras for initial installations