buildbot exception in on flink-docs-release-1.0

[buildbot]

The Buildbot has detected a build exception on builder flink-docs-release-1.0 
while building . Full details are available at:
    https://ci.apache.org/builders/flink-docs-release-1.0/builds/41

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

Buildslave for this Build: orcus_ubuntu

Build Reason: forced: by IRC user <uce> on channel #flink-testing: build me the 
docs please
Build Source Stamp: HEAD
Blamelist: 

BUILD FAILED: exception git

Sincerely,
 -The Buildbot