load_and_validate_raw_contents catches syntax errors

Catch SyntaxError exceptions such as Psych::SyntaxError. …
#210

Note:  YAML::SyntaxError/Psych::SyntaxError exceptions are NOT StandardError exceptions
so they must be caught in addition to StandardError.

irb(main):003:0> YAML::SyntaxError.ancestors
=> [Psych::SyntaxError, SyntaxError, ScriptError, Exception, ActiveSupport::Dependencies::Blamable, Object, PP::ObjectMixin, Vmdb::GlobalMethods, MoreCoreExtensions::ObjectNamespace, JSON::Ext::Generator::GeneratorMethods::Object, ActiveSupport::Dependencies::Loadable, Kernel, BasicObject]
`return`?