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/201

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

Buildslave for this Build: bb_slave8_ubuntu

Build Reason: The Nightly scheduler named 'openjpaNightly-master' triggered 
this build
Build Source Stamp: [branch openjpa/master] HEAD
Blamelist: 

BUILD FAILED: exception git

Sincerely,
 -The Buildbot