Same error message as T4313, though I suspect different cause. Public installation, so please feel free to poke at it if it's in any way helpful.

I have an external repository imported through Diffusion (http://phabricator.freedesktop.org/diffusion/FDOWAY/) which is not being republished through Phabricator itself. This is associated with the project (as in, /projects/) 'Wayland'. Trying to import symbols with import_project_symbols.php gives me:

phabricator@fk01:/srv/phabricator.fooishbar.org/git/CHECKOUT-wayland-fdo$ find ./ -type f -name '*.[ch]' | ../../phabricator/scripts/symbols/generate_ctags_symbols.php | ../../phabricator/scripts/symbols/import_project_symbols.php --trace wayland
>>> [2] <connect> phabricator_repository
<<< [2] <connect> 1,323 us
>>> [3] <query> SELECT * FROM `repository_arcanistproject` WHERE name = 'wayland'  
<<< [3] <query> 220 us  
Project 'wayland' is unknown. Upload a diff to implicitly create it.

Sure enough, looking in /repositories/ shows the two repositories I've imported through Diffusion in the first section, but no Arcanist projects. Going through the 'Create New ...' workflow doesn't give me an Arcanist project (I just tried), nor does creating diffs through 'arc diff' (there are several revisions submitted against both repositories already).

What gives?