On a Mac, also on NetBSD or OpenBSD, `touch` errs differently:
```
$ uname; touch a/b/c
Darwin
touch: a/b/c: No such file or directory
```
That gets matched by the rule but not fixed by it. Thus the regex
pattern is now a bit more tolerant.
Move them to `rules` sub-directory and import `shells` instead of `and_`
which in turn triggers the `generic_shell` fixture fixing the tests on
Fish Shell.