Hide stack trace shown on YAML parse error by default

[whym]

A YAML parse error is not caused by the podman-compose code, and the stack trace will not be helpful
in a typical use case. Adding --verbose will still show it, for those who need it.

Fixes #1139

Some questions I have:

• I chose log.fatal() for the parse error message that is always shown. Is it a good choice? Some parts of the code use it, others use sys.stderr.write(), for things like this.
• I don't know if we should let it die in resolve_extends() or try to catch error and return {} in that case. I left the behavior unchanged for now.

EDIT: wrong issue number

[p12tic]

obvious comment -> remove

[p12tic]

obvious comment -> remove

[p12tic]

I chose log.fatal() for the parse error message that is always shown. Is it a good choice? Some parts of the code use it, others use sys.stderr.write(), for things like this.

I think this is historical artifact. I would prefer consistent use of log.fatal()

I don't know if we should let it die in resolve_extends() or try to catch error and return {} in that case. I left the behavior unchanged for now.

I think using sys.exit() is bad practice. If you want to spend time on fixing this, let's do it in another PR.

[p12tic]

Some nits, also please add a newsfragment.

[p12tic]

Rebased and squashed related commits.