dashboard login fails with "CSRF cookie not set. Cookies may be turned off. Make sure cookies are enabled and try again."

[Corey Bryant]

ubuntu@node-mees:~$ snap list microstack
Name Version Rev Tracking Publisher Notes
microstack ussuri 232 latest/edge canonical✓ devmode

Attempt to login to dashboard fails with error message "CSRF cookie not set. Cookies may be turned off. Make sure cookies are enabled and try again." See attached screenshot. It seems this is an intermittent error as an ensuing login attempt is successful.

At first I thought adding SESSION_COOKIE_HTTPONLY = True to /var/snap/microstack/common/etc/horizon/local_settings.d/_05_snap_tweaks.py and restarting horizon [1] helped but it seems that it's intermittent. And besides, SESSION_COOKIE_HTTPONLY defaults to True in Ussuri.
[1] sudo systemctl restart snap.microstack.horizon-uwsgi.service

Further reference:
https://docs.openstack.org/security-guide/dashboard/cookies.html