Error: cannot set terminal process group (-1): Inappropriate ioctl for device

When I have `dumb-init` in `ENTRYPOINT` like this

```
...
ENTRYPOINT ["/usr/bin/dumb-init"]
...
```

and then try to run `bash` with `tty` and interactively, I get this error:

```
docker run --rm -t -i dumb_init_image bash
bash: cannot set terminal process group (-1): Inappropriate ioctl for device
...
```
