r218344 <http://trac.webkit.org/changeset/218344> caused thousands of layout test crashes due to the update on WPEBackend-mesa on the JHBuild.
My guess is that something is setting a DISPLAY environment there (perhaps the tool driver) and confusing the check for X11.
The bot itself doesn't set that variable.
Committed r218355: <http://trac.webkit.org/changeset/218355>
I reverted the update on WPEBackend-mesa that triggered this issue. Layout tests are working back as expected on WPE.
Also I identified the issue: we are setting always a DISPLAY environment variable on Tools/Scripts/webkitpy/port/base.py (even when the user environment doesn't have one).
I will upload ASAP a patch to fix this.
Proposed patch at: bug 173483
Committed r218491: <http://trac.webkit.org/changeset/218491>