Returns a (method, path, version) tuple for an HTTP 1.x request line.

    The response is a `collections.namedtuple`.

    >>> parse_request_start_line("GET /foo HTTP/1.1")
    RequestStartLine(method='GET', path='/foo', version='HTTP/1.1')

def parse_request_start_line(line: str) -> RequestStartLine:
    """Returns a (method, path, version) tuple for an HTTP 1.x request line.

    The response is a `collections.namedtuple`.

    >>> parse_request_start_line("GET /foo HTTP/1.1")
    RequestStartLine(method='GET', path='/foo', version='HTTP/1.1')
    """
    try:
        method, path, version = line.split(" ")
    except ValueError:
        # https://tools.ietf.org/html/rfc7230#section-3.1.1
        # invalid request-line SHOULD respond with a 400 (Bad Request)
        raise HTTPInputError("Malformed HTTP request line")
    if not re.match(r"^HTTP/1\.[0-9]$", version):
        raise HTTPInputError(
            "Malformed HTTP version in HTTP Request-Line: %r" % version
        )
    return RequestStartLine(method, path, version)