buildbot exception in MacPorts on ports-10.6_x86_64_legacy-watcher

[buildbot at macports.org]

The Buildbot has detected a build exception on builder ports-10.6_x86_64_legacy-watcher while building MacPorts. Full details are available at:
    https://build.macports.org/builders/ports-10.6_x86_64_legacy-watcher/builds/21522

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

Buildslave for this Build: ports-10.6_x86_64_legacy

Build Reason: A build was forced by 'devans <devans at localhost>': force build
Build Source Stamp: HEAD
Blamelist: 

BUILD FAILED: exception

Sincerely,
 -The Buildbot