Poudriere errors encountered gathering ports metadata

[Miroslav Lachman]

I am trying to rebuild ports for my PC-BSD based desktop computer.

Options went fine:
    poudriere options -z pcbsd -p pcbsd-head -f 
/usr/local/etc/poudriere.d/pkglists/pcbsd

But when I run bulk I always get this error

    poudriere bulk -vv -j 10_4_amd64 -z pcbsd -p pcbsd-head -f 
/usr/local/etc/poudriere.d/pkglists/pcbsd

[00:00:06] Error: Fatal errors encountered gathering ports metadata

For example:

[00:00:06] x11-toolkits/gtk30 depends on x11/libXinerama
[00:00:06] x11-toolkits/gtk30 depends on x11/libXrandr
[00:00:06] x11-toolkits/gtk30 depends on x11/libXrender
[00:00:06] Warning: (x11-toolkits/gtk30): [00:00:06] Debug: 
gather_port_vars_port (x11-toolkits/gtk30): Adding to depqueue
[00:00:06] Error: Fatal errors encountered gathering ports metadata
[00:00:06] Cleaning up
10_4_amd64-pcbsd-head-pcbsd: removed
10_4_amd64-pcbsd-head-pcbsd-n: removed
[00:00:06] Unmounting file systems

If I remove x11-toolkits/gtk30 from the ports list then I got this error 
for another one.

What this error means and how can I debug it?

Kind regards
Miroslav Lachman