Transition from PyYAML to ruamel.yaml

[andy-maier]

Transition from PyYAML to ruamel.yaml

Reasons in favor of making the transition:

• PyYAML currently has 202 issues open and 87 PRs open. ruamel.yaml has 108 open issues and 0 open merge requests.
• In the last 2 years, PyYAML had only one release (6.0.1), while ruamel.yaml has had 24 releases.
• Using PyYAML to create OrderedDict objects from YAML dicts requires using an extra package "yamlloader", and it is not clear how that can be combined with the PyYAML safe_load() method. However, on Python >=3.6, dict is ordered, so yamlloader is no longer needed.
• The PyYAML documentation is quite terse.
• Due to various issues, some versions of PyYAML need to be excluded:

PyYAML>=5.3.1,!=5.4.0,!=5.4.1,!=6.0.0

Reasons for not making the transition (yet):

• ruamel.yaml is still below 1.0 and states dev status "4 - Beta".