Our chamuyero tests involve reading and writing utf8. This usually
works, but is dependent on the environment: on LC_ALL=POSIX environment,
for example, Python enforces ascii as the default encoding, and the
tests break.
So this patch makes chamuyero explicitly set utf8 encodings in stdout
and all the sockets.
This patch adds a new integration test, which executes various small
dialogs, to cover corner cases that are not well covered (according to
our coverage report).
For example, "EHLO" without domain, or invalid DATA.
While we could do them via Go tests, this way is more realistic, and the
tests are easier to write.
This patch adds "chamuyero", a a tool to test and validate line-oriented
commands and servers.
It can launch and communicate with other processes, and follow a script of
line-oriented request-response, validating the dialog as it goes along.
This can be used to test line-oriented network protocols (such as SMTP) or
interactive command-line tools.
It will be used in follow up patches to test new commands and
functionality.
