[gerrit_util] Add note about workaround

Bug: b/349433100
Change-Id: I287499a339e1f5d3eab9c5a63068ad68ecd67a11
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5677617
Commit-Queue: Yiwei Zhang <yiwzhang@google.com>
Reviewed-by: Yiwei Zhang <yiwzhang@google.com>
Auto-Submit: Allen Li <ayatane@chromium.org>

gerrit_util.py

@@ -507,7 +507,9 @@ class SSOAuthenticator(Authenticator):
         # Finally, add cookies
         sso_info.cookies.add_cookie_header(conn)
         assert 'Cookie' in conn.req_headers, (
-            'sso_info.cookies.add_cookie_header failed to add Cookie')
+            'sso_info.cookies.add_cookie_header failed to add Cookie'
+            ' (try running `git ls-remote sso://chromium/All-Projects` and retrying)'
+        )
 
     def debug_summary_state(self) -> str:
         return ''