Bad error reporting on create type

CREATE TYPE MyStr EXTENDING str;                                     
ERROR: InternalServerError: 'NoneType' object has no attribute 'is_schema_field'

Version 1.0-alpha.2+dev.391.g2276144b

I obviously needed CREATE SCALAR TYPE and would expect it to be grammar error (i.e. something like TYPE is unexpected, expected one of SCALAR, DATABASE, ...

[elprans]

would expect it to be grammar error

CREATE TYPE is valid syntax and is used to define object types. The crash in this case is caused by the fact that you’re trying to create an object type that inherits from a scalar type. There has to be a check to prevent mixing schema object classes like that. Here and here are good spots to place the checks in (check bases).

[msullivan]

It looks like we produce an error message now (instead of an ISE), but not a good one: ERROR: InvalidReferenceError: schema object UUID('00000000-0000-0000-0000-000000000101') exists, but is a 'scalar type' not a 'object type'

We can do better