DUNE should not fail silently - Docker `execute_cmd_*` rework

[wackou]

This refactors a bit the various docker::execute_cmd_* methods in order to have a single, generic and flexible one that can be called by other specialized ones if needed.

I also added an option to be able to have colored output outside the docker process (this is my main motivation for the PR!) cmake build and test benefit from that for instance.

Also, by default the dune executable will also fail if a docker.execute_cmd() fails, which ensures we do not fail silently in certain cases and go on. This can be deactivated by passing the check_status=False option.

[wackou]

Thanks for the PR. I'm not convinced in adding new docker_error exception, but the rest looks good.

So, I added the docker_error because I needed to propagate an exception, but dune_error wasn't available here, and it cannot be imported because it is dune.py that imports docker.py. I wasn't 100% convinced it was the best choice either. I see the following options:

• use docker_error as of now
• move dune_error to a different file that can be imported by both dune.py and docker.py (but I'm not sure that dune_error and docker_error have the same semantics, i.e. are supposed to represent the same type of errors)
• call check_returncode on the completed process and let a CalledProcessError propagate (see: https://docs.python.org/3/library/subprocess.html#subprocess.CompletedProcess.check_returncode) (but then we can't print stdout/stderr before raising the exception)
• something else?

Let me know which solution you prefer the best, or if you have any other suggestion, and I'll implement that.

Thanks!