CLI robustness

[mahmoud]

Python doesn't have a great track record of CLIs that handle piping well. Basically, we need to break that mold and make sure that when glom plays nicely in shell pipelines.

Some links on the topic:

• https://stackoverflow.com/questions/14207708/ioerror-errno-32-broken-pipe-python/30091579#30091579
• https://stackoverflow.com/questions/16314321/suppressing-printout-of-exception-ignored-message-in-python-3/34299346
• A bit of a counterexample: Handle SIGPIPE in click.echo(). pallets/click#626

face middleware should make it easy to semi-contextually catch the error, register a different signal handler, or even inject wrapped stdin/stdout handles.