gaurav@ubuntu:~/fresh_instantbird/instantbird$ python client.py checkout
Executing command: ['hg', 'pull', '-R', './.']
pulling from http://hg.instantbird.org/instantbird
searching for changes
no changes found
Executing command: ['hg', 'update', '-v', '-r', 'default', '-R', './.']
resolving manifests
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
Updated to revision ceb11e06a1fca3cf3478624b173cc34524a1162d.
Executing command: ['hg', 'pull', '-R', './mozilla', 'http://hg.mozilla.org/releases/mozilla-release/']
pulling from http://hg.mozilla.org/releases/mozilla-release/
searching for changes
no changes found
Executing command: ['hg', 'update', '-v', '-r', 'FIREFOX_11_0_RELEASE', '-R', './mozilla']
abort: crosses branches (merge branches or use --clean to discard changes)
Traceback (most recent call last):
  File "client.py", line 190, in <module>
    do_hg_pull('mozilla', options.mozilla_repo, options.hg, options.mozilla_rev)
  File "client.py", line 83, in do_hg_pull
    check_call_noisy(cmd)
  File "client.py", line 44, in check_call_noisy
    check_call(cmd, *args, **kwargs)
  File "/usr/lib/python2.7/subprocess.py", line 511, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['hg', 'update', '-v', '-r', 'FIREFOX_11_0_RELEASE', '-R', './mozilla']' returned non-zero exit status 255