Troublshooting guix-publish make-systemd-constructor

[Jack Hill]

Hi Guix,

I have the following in my operating system services:
(service guix-publish-service-type
         (guix-publish-configuration
          (port 9090)
          (host "localhost")))


However, trying to connect to port 9090 from localhost hangs.

`ss -tunlp | grep 9090` shows shepherd listening however:

tcp   LISTEN 0      128                          127.0.0.1:9090       0.0.0.0:*    
users:(("shepherd",pid=1,fd=23))

I could use some tips on what's wrong with guix-publish, and more 
generally how to troubleshoot systemd services.

Thanks!
Jack