def _get_update_status(env: Environment) -> Optional[str]:
    """If there is a new update available, return the warning text.
    Otherwise just return None."""
    file = env.config.version_info_file
    if not file.exists():
        return None

    with _get_suppress_context(env):
        # If the user quickly spawns multiple httpie processes
        # we don't want to end in a race.
        with open_with_lockfile(file) as stream:
            version_info = json.load(stream)

        available_channels = version_info['last_released_versions']
        if BUILD_CHANNEL not in available_channels:
            return None

        current_version = httpie.__version__
        last_released_version = available_channels[BUILD_CHANNEL]
        if not is_version_greater(last_released_version, current_version):
            return None

        text = UPDATE_MESSAGE_FORMAT.format(
            last_released_version=last_released_version,
            installation_method=BUILD_CHANNEL,
        )
        return text
If there is a new update available, return the warning text.
    Otherwise just return None.
httpie/internal/update_warnings.py