Xvfb PyQt5 Xlib: расширение RANDR отсутствует на дисплее

Я пытаюсь запустить untitests для своего приложения PyQt5 на Jenkins.

Я настроил задание и настроил Xvfb с опцией +extension RANDR

Вот результат запуска Xvfb:

Xvfb starting$ Xvfb -displayfd 2 -screen 0 1280x1024x24 -fbdir /var/lib/jenkins/2014-08-27_00-24-501722001619127938033xvfb +extension RANDR
_XSERVTransSocketUNIXCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
Initializing built-in extension Generic Event Extension
Initializing built-in extension SHAPE
Initializing built-in extension MIT-SHM
Initializing built-in extension XInputExtension
Initializing built-in extension XTEST
Initializing built-in extension BIG-REQUESTS
Initializing built-in extension SYNC
Initializing built-in extension XKEYBOARD
Initializing built-in extension XC-MISC
Initializing built-in extension SECURITY
Initializing built-in extension XINERAMA
Initializing built-in extension XFIXES
Initializing built-in extension RENDER
Initializing built-in extension RANDR
Initializing built-in extension COMPOSITE
Initializing built-in extension DAMAGE
Initializing built-in extension MIT-SCREEN-SAVER
Initializing built-in extension DOUBLE-BUFFER
Initializing built-in extension RECORD
Initializing built-in extension DPMS
Initializing built-in extension Present
Initializing built-in extension DRI3
Initializing built-in extension X-Resource
Initializing built-in extension XVideo
Initializing built-in extension XVideo-MotionCompensation
Initializing built-in extension SELinux
Initializing built-in extension GLX
1 

Но мои тесты графического интерфейса терпят неудачу с Xlib: extension "RANDR" missing on display ":1".

Как я могу это исправить? Есть ли другой способ запустить юнит-тест графического интерфейса PyQt5?

Я просмотрел этот вопрос, но это не помогло

Я использую Ubuntu 14.04.1 x86_64; питон3.4