Os status codes na faixa dos 400 significam que houve um erro por parte do cliente.

Você se lembra de todos aqueles erros (e piadas) a respeito do "**404 Not Found**"?

## Use o `HTTPException`

Para retornar ao cliente *responses* HTTP com erros, use o `HTTPException`.

### Import `HTTPException`

```Python hl_lines="1"
{!../../../docs_src/handling_errors/tutorial001.py!}
```

```
1 validation error
path -> item_id
  value is not a valid integer (type=type_error.integer)
```

#### `RequestValidationError` vs. `ValidationError`

!!! warning "Achtung"
    Das folgende sind technische Details, die Sie überspringen können, wenn sie für Sie nicht wichtig sind.

def test_override_server_error_exception_raises():
    with pytest.raises(RuntimeError):
        client.get("/server-error")


def test_override_server_error_exception_response():
    client = TestClient(app, raise_server_exceptions=False)
    response = client.get("/server-error")
    assert response.status_code == 500

@router.get("/a", responses={501: {"description": "Error 1"}})
async def a():
    return "a"


@router.get(
    "/b",
    responses={
        502: {"description": "Error 2"},
        "4XX": {"description": "Error with range, upper"},
    },
)
async def b():
    return "b"


@router.get(
    "/c",
    responses={
        "400": {"description": "Error with str"},

                {
                    "loc": ["path", "item_id"],
                    "msg": "value is not a valid integer",
                    "type": "type_error.integer",
                }
            ]
        }
    )


def test_get_http_error():
    response = client.get("/items/3")
    assert response.status_code == 418, response.text
    assert response.json() == {"detail": "Nope! I don't like 3."}

        client.get("/model/modelX")
    assert err.value.errors() == [
        IsDict(
            {
                "type": "value_error",
                "loc": ("response", "name"),
                "msg": "Value error, name must end in A",
                "input": "modelX",
                "ctx": {"error": HasRepr("ValueError('name must end in A')")},
            }
        )
        | IsDict(

                    "loc": ["body", "file"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "fileb"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "token"],

    assert response.json() == {"detail": "Item not found"}


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == {
        "openapi": "3.1.0",
        "info": {"title": "FastAPI", "version": "0.1.0"},
        "paths": {
            "/items/{item_id}": {
                "get": {

                    "loc": ["body", "item"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "user"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["body", "importance"],

                    "loc": ["query", "needy"],
                    "msg": "field required",
                    "type": "value_error.missing",
                },
                {
                    "loc": ["query", "skip"],
                    "msg": "value is not a valid integer",
                    "type": "type_error.integer",
                },
                {
                    "loc": ["query", "limit"],