message: The warning in read_front_buffer is intentional
diff: @@ -524,6 +524,8 @@ impl Context {
  let dimensions = self.get_framebuffer_dimensions();
  let rect = ::Rect { left: 0, bottom: 0, width: dimensions.0, height: dimensions.1 };
  + // FIXME: See https://github.com/glium/glium/pull/1682#issuecomment-375596152
  + // Leave it unchecked for now, it will generate warning as a reminder it needs fixing.
  let mut data = Vec::with_capacity(0);
  ops::read(&mut ctxt, ops::Source::DefaultFramebuffer(gl::FRONT_LEFT), &rect,
  &mut data, false);
  