Implement a smoke test like flask-shell-bpython

In `flask-shell-bpython` I was able to write a simple smoke test that Travis can execute: https://github.com/jacquerie/flask-shell-bpython/blob/18a1aaed34189a6f190ba424304000e8f153efde/run-tests.sh#L6-L14

I couldn't do it here because `ptpython` detects that `stdin` is not a `tty` and refuses to start. Perhaps I can use `expect` (https://en.wikipedia.org/wiki/Expect) ?