Bug #1908607: Fixjson to_primitive when using IO OBjects.

Remove the yamlutils, the pyyaml is now safe by default.

Theyamlutils module is deprecated in Ussuri andsupport will be removed in a future release.

Support for Python 2.7 has been dropped. The minimum version of Python nowsupported is Python 3.6.

Introduce reno for deployer release notes.