The default value is what python's sys.getfilesystemencoding() returns, which on Windows is 'mbcs', on Mac OSX is 'utf-8', and on Unix depends on your locale settings.
If you need a different encoding, this can be changed in your build slave's
buildbot.tac file by adding a unicode_encoding argument to BuildSlave:
Setting allow_shutdown to 'file' will cause the buildslave to watch 'shutdown.stamp' in basedir for updates to its mtime. The file does not need to exist prior to starting the slave.
Setting allow_shutdown to 'signal' will set up a SIGHUP handler to start a graceful shutdown.
The default value is None, in which case this feature will be disabled.
Both master and slave must be at least version 0.8.3 for this feature to work.
s = BuildSlave(buildmaster_host, port, slavename, passwd, basedir, keepalive, usepty, umask=umask, maxdelay=maxdelay, unicode_encoding='utf-8', allow_shutdown='signal')