Take a stab at fixing CI

[zenhack]

The docker image does not actually contain bash, which is the source of the error we're seeing checkout. So an obvious thing to try is to use the shell that is there, which is what this patch does. crosses fingers

[zenhack]

Drat, that didn't work. Closing.

(I looked, and it looked like bash is there, just not at /bin/bash as I was expecting).

[easye]

The canonical way to get around this is get env to invoke bash:

#!/usr/bin/env bash