add is_version in tools

    # revert preparation of chroot

    unprepare_chroot(path, mount)

def is_version(version):

    '''

    Check if version is valid

    '''

    if re.match("^(\d+)(?:([-~+]).*)?$", version) is None:

        raise TypeError("Invalid version format %s" % buf)

def compare_versions(v1, v2):

    '''

    This function compare version :param v1: and version :param v2: