buildbot exception in MacPorts on ports-10.12_x86_64-watcher

[buildbot at macports.org]

The Buildbot has detected a build exception on builder ports-10.12_x86_64-watcher while building macports/macports-ports. Full details are available at:
    https://build.macports.org/builders/ports-10.12_x86_64-watcher/builds/38606

Buildbot URL: https://build.macports.org/

Buildslave for this Build: ports-10.12_x86_64

Build Reason: The SingleBranchScheduler scheduler named 'ports' triggered this build
Build Source Stamp: [branch master] 889b95ac250f502cee545e36f5f07b353d721bf5
Blamelist: Steven Thomas Smith <s.t.smith at ieee.org>

BUILD FAILED: exception

Sincerely,
 -The Buildbot