Improve uncaught PydanticUseDefault exception message (#1730)

Author: Viicos

src/errors/validation_exception.rs

@@ -110,7 +110,7 @@ impl ValidationError {
     }
 
     pub fn use_default_error() -> PyErr {
-        py_schema_error_type!("Uncaught UseDefault error, please check your usage of `default` validators.")
+        py_schema_error_type!("Uncaught `PydanticUseDefault` exception: the error was raised in a field validator and no default value is available for that field.")
     }
 
     fn maybe_add_cause(self_: PyRef<'_, Self>, py: Python) -> Option<PyErr> {

tests/validators/test_with_default.py

@@ -627,12 +627,18 @@ def val_func(v: Any, handler: core_schema.ValidatorFunctionWrapHandler) -> Any:
     validator = SchemaValidator(
         core_schema.with_default_schema(core_schema.no_info_wrap_validator_function(val_func, core_schema.int_schema()))
     )
-    with pytest.raises(SchemaError, match='Uncaught UseDefault error, please check your usage of `default` validators'):
+    with pytest.raises(
+        SchemaError,
+        match='Uncaught `PydanticUseDefault` exception: the error was raised in a field validator and no default value is available for that field.',
+    ):
         validator.validate_python('')
 
     # same if there is no WithDefault validator
     validator = SchemaValidator(core_schema.no_info_wrap_validator_function(val_func, core_schema.int_schema()))
-    with pytest.raises(SchemaError, match='Uncaught UseDefault error, please check your usage of `default` validators'):
+    with pytest.raises(
+        SchemaError,
+        match='Uncaught `PydanticUseDefault` exception: the error was raised in a field validator and no default value is available for that field.',
+    ):
         validator.validate_python('')