buildbot failure in Verilog-to-Routing (VTR) on nightly

[buil...@picton.eecg.toronto.edu]

The Buildbot has detected a new failure on builder nightly while building Verilog-to-Routing (VTR).
Full details are available at:
builds.verilogtorouting.org:8080/builders/nightly/builds/1072

Buildbot URL: builds.verilogtorouting.org:8080/

Buildslave for this Build: slave_nightly

Build Reason: The Nightly scheduler named 'scheduler_nightly' triggered this build
Build Source Stamp: [branch master] HEAD
Blamelist:

BUILD FAILED: failed vtr_reg_nightly

sincerely,
-The Buildbot