buildbot exception in Mercurial on hg tests

[hgbuildbot at kublai.com]

The Buildbot has detected a new failure on builder hg tests while building hg.
Full details are available at:
 http://hgbuildbot.kublai.com/builders/hg%20tests/builds/308

Buildbot URL: http://hgbuildbot.kublai.com/

Buildslave for this Build: l6

Build Reason: scheduler
Build Source Stamp: [branch default] d51364b318eab1871af13f30be099799c04a43d1
Blamelist: Angel Ezquerra <angel.ezquerra at gmail.com>

BUILD FAILED: exception

sincerely,
 -The Buildbot