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/26771

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] e589aee078f1500ac2b5e0455ea5819662c7de56
Blamelist: Blair Zajac <blair at macports.org>

BUILD FAILED: exception

Sincerely,
 -The Buildbot