buildbot exception in on openjpa-master-docs

[buildbot]

The Buildbot has detected a build exception on builder openjpa-master-docs 
while building . Full details are available at:
    https://ci.apache.org/builders/openjpa-master-docs/builds/585

Buildbot URL: https://ci.apache.org/

Buildslave for this Build: bb_slave8_ubuntu

Build Reason: forced: by IRC user <struberg> (privmsg): None
Build Source Stamp: HEAD
Blamelist: 

BUILD FAILED: exception interrupted

Sincerely,
 -The Buildbot