request.stdin stream manipulation breaks when used under gunicorn

[LadyNamedLaura]

_get_request_from_request(request):¹ tries to do:

    body_pos = request.stdin.tell()
    request.stdin.seek(0)
    body = request.stdin.read()
    request.stdin.seek(body_pos)

However, it seems like under gunicorn this request.stdin doesn't have the tell method. (nor the seek method)²
Given that neither body_pos nor body seem to be used in that method, I'd suggest removing those 4 lines to make this code compatible with gunicorn. (or somehow check if tell is available)

¹ https://github.com/collective/collective.sentry/blob/master/collective/sentry/error_handler.py#L90-L93
¹ https://github.com/benoitc/gunicorn/blob/master/gunicorn/http/body.py#L177