I can't create Almanac Namespace

Reproduce
Install totally new instance or run it in docker, then go to Almanac and try create new Namespace
Version

root@f1743f6a678a:/var/www/arcanist/bin# ./arc version
arcanist 4b3baca999a4a229433c891cf69c2c4e2d634b89 (16 Oct 2020)

Duplicate of https://discourse.phabricator-community.org/t/i-cant-create-almanac-space/4424.