buildbot exception in MacPorts on ports-10.7_x86_64_legacy-watcher

[buildbot at macports.org]

The Buildbot has detected a build exception on builder ports-10.7_x86_64_legacy-watcher while building macports/macports-ports. Full details are available at:
    https://build.macports.org/builders/ports-10.7_x86_64_legacy-watcher/builds/20599

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

Buildslave for this Build: ports-10.7_x86_64_legacy

Build Reason: The SingleBranchScheduler scheduler named 'ports' triggered this build
Build Source Stamp: [branch master] d5a2a26c198073694c5b00a124738e139c8c02e1
Blamelist: Joshua Root <jmr at macports.org>

BUILD FAILED: exception

Sincerely,
 -The Buildbot