This was sometimes slightly annoying in porting.
5 is enough most of the time, 10 should be enough basically always,
without being too annoying if you don't need it.
Make it easier to use pexpect and to understand its error messages.
Switch to a style in tests using bound methods, which makes them
less noisy to write.
This adds a new interactive test framework based on Python's pexpect. This
is intended to supplant the TCL expect-based tests.
New tests go in `tests/pexpects/`. As a proof-of-concept, the
pipeline.expect test and the (gnarly) bind.expect test are ported to the
new framework.
