catch PydanticUndefinedAnnotation in create_response_field

this exception may be raised when having some unresolvable forward refs
most probably when trying to return a complex SQLAlchemy object

fastapi/_compat.py

@@ -47,6 +47,7 @@ sequence_types = tuple(sequence_annotation_to_type.keys())
 
 if PYDANTIC_V2:
     from pydantic import PydanticSchemaGenerationError as PydanticSchemaGenerationError
+    from pydantic.errors import PydanticUndefinedAnnotation as PydanticUndefinedAnnotation
     from pydantic import TypeAdapter
     from pydantic import ValidationError as ValidationError
     from pydantic._internal._schema_generation_shared import (  # type: ignore[attr-defined]
@@ -358,6 +359,9 @@ else:
     class PydanticSchemaGenerationError(Exception):  # type: ignore[no-redef]
         pass
 
+    class PydanticUndefinedAnnotation(Exception):  # type: ignore[no-redef]
+        pass
+
     def with_info_plain_validator_function(  # type: ignore[misc]
         function: Callable[..., Any],
         *,

fastapi/utils.py

@@ -20,6 +20,7 @@ from fastapi._compat import (
     BaseConfig,
     ModelField,
     PydanticSchemaGenerationError,
+    PydanticUndefinedAnnotation,
     Undefined,
     UndefinedType,
     Validator,
@@ -97,7 +98,7 @@ def create_response_field(
         )
     try:
         return ModelField(**kwargs)  # type: ignore[arg-type]
-    except (RuntimeError, PydanticSchemaGenerationError):
+    except (RuntimeError, PydanticSchemaGenerationError, PydanticUndefinedAnnotation):
         raise fastapi.exceptions.FastAPIError(
             "Invalid args for response field! Hint: "
             f"check that {type_} is a valid Pydantic field type. "