perl-Gtk3-0.017-1.fc22 fails to build in F22 if TCP port 6666 is already used: + xinit /bin/sh -c 'rm -f ok; make test && touch ok' -- /usr/bin/Xvfb :666 _XSERVTransSocketINETCreateListener: ...SocketCreateListener() failed _XSERVTransMakeAllCOTSServerListeners: server already running (EE) Fatal server error: (EE) Cannot establish any listening sockets - Make sure an X server isn't already running(EE) XIO: fatal IO error 11 (Resource temporarily unavailable) on X server ":666" after 7 requests (7 known processed) with 0 events remaining. + test -e ok Using xvfb-run tool instead of manually specifying display number should fix it.