Works fine on macOS; blows up on Linux.
fixes:
```
/bin/bash: - : invalid option
Usage: /bin/bash [GNU long option] [option] ...
/bin/bash [GNU long option] [option] script-file ...
```
Admittedly it's overkill to use RSpec to run a set of assertions against
a DNS server -- a simple shell script would have been shorter and more
understandable. We are using RSpec merely to practice using RSpec.
Also, RSpec is not quite appropriate because we're not testing a Ruby
class. In fact, we're not test Ruby code at all. So we should not be
using RSpec. Just sayin'.
