'makes a new bzr branch if it does not already exist'

def clone(self):

    dest_dirname = os.path.dirname(self.dest)
    try:
        os.makedirs(dest_dirname)
    except:
        pass
    if (self.version.lower() != 'head'):
        args_list = ['branch', '-r', self.version, self.parent, self.dest]
    else:
        args_list = ['branch', self.parent, self.dest]
    return self._command(args_list, check_rc=True, cwd=dest_dirname)
