Try “echo hi” instead. Could be the working directory where the command is run is a directory that the HA user can’t access. Other than that can’t help you much since I don’t use HASSIO.
As best I can tell that error message happens when the command returns a non-zero exit status. Of course, “echo hi” probably shouldn’t be doing that, so it would seem to have more to do with the context HASSIO runs these commands in, which again, unfortunately, I know nothing about. You might want to start a new topic specific to your situation to which others with more pertinent knowledge might reply.