Feature Request: Improve error message for "can't find enum" warning

[parker-research]

The def finalize(self): method in RewritePybind11EnumValueRepr is a bit confusing.

I wish it explained why it couldn't automatically locate the "enum class location". I'd prefer not to have to hardcode the --enum-class-locations argument in the build yml.

Update: It seems that my issue is related to an enum containing a "None_" value. It works when that value is commented out in the bindings, but fails when the value is included in the Enum.