Unable to source byobu-reconnect-sockets with fish-shell

[Jeffrey04]

In order to source the script in fish, I used https://github.com/edc/bass and issued the command

```
> bass . /usr/bin/byobu-reconnect-sockets -i

ERROR: You must source this file, rather than execute it.
  . bass
```

The error came from this check

```
case "$-" in
       *i*)
               # no-op
       ;;
       *)
               echo 2>&1
               echo "ERROR: You must source this file, rather than execute it." 2>&1
               echo " . $0" 2>&1
               echo 2>&1
               exit 1
       ;;
esac
```

After commenting the block of code, it would work as expected. Is it possible to not make the check so strict, or is it possible to make the script usable for other shells too?

```
> byobu --version
byobu version 5.133
tmux 3.0a
> fish --version
fish, version 3.1.0
```