Problem:
`feed_command()` was added as a "bridge" for old test code. 99% of those
cases should be using `n.command()`, which raises errors instead of
silently continuing the test.
Solution:
Deprecate `feed_command()`. It should not be used in new tests.
All usages of `feed_command()` should be converted to `command()` or
`feed()`.
afdad5c76e
