buildbot failure in on singa-site-staging

[buildbot]

The Buildbot has detected a new failure on builder singa-site-staging while 
building . Full details are available at:
    https://ci.apache.org/builders/singa-site-staging/builds/139

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

Buildslave for this Build: bb-cms-slave

Build Reason: The AnyBranchScheduler scheduler named 'on-singa-site-commit' 
triggered this build
Build Source Stamp: [branch incubator/singa/site] 1756352
Blamelist: wangwei

BUILD FAILED: failed compile

Sincerely,
 -The Buildbot