diff --git a/src/pip/_internal/download.py b/src/pip/_internal/download.py
index 3513b67ea1d..567b3874569 100644
--- a/src/pip/_internal/download.py
+++ b/src/pip/_internal/download.py
@@ -652,7 +652,10 @@ def __init__(self, *args, **kwargs):
         elif _KERBEROS_AVAILABLE and not prompting:
             auths = [no_prompt, HTTPKerberosAuth(ik.REQUIRED)]
         else:
-            auths = [MultiDomainBasicAuth(prompting=prompting, index_urls=index_urls)]
+            auths = [MultiDomainBasicAuth(
+                prompting=prompting,
+                index_urls=index_urls
+            )]
 
         self.auth = MultiAuth(*auths)