python-hyper/community

So you're totally right; the issue is in this function: https://github.com/python-hyper/h11/blob/master/h11/_readers.py#L35

Thank you for advice about the desired spot, I feel so stupid!

I rewrote _obsolete_line_fold a bit:

def _obsolete_line_fold(lines):
    it = iter(lines)
    last = None
    for line in it:
        match = obs_fold_re.match(line)
        if match:
            if last is None:
                raise LocalProtocolError("continuation line at start of headers")
            if not isinstance(last, bytearray):
                last = bytearray(last)

            while last.endswith(b"\r"):  # change is here
                del last[-1]             # and there

            last += b" "
            last += line[match.end() :]
        else:
            if last is not None:
                yield last
            last = line
    if last is not None:
        while last.endswith(b"\r"):  # change is here
            del last[-1]  # and there

        yield last

I assume that if assert isinstance(last, bytearray), then we can just remove the end of the bytearray (please correct me if I'm wrong, but it shouldn't cause an extra alloc).