chore: use HTTP_422_UNPROCESSABLE_CONTENT instead of literal 422

Use HTTP_422_UNPROCESSABLE_CONTENT wherever literal 422 was used in
fastapi/fastapi#14077.

docs_src/handling_errors/tutorial005_py310.py

@@ -1,4 +1,4 @@
-from fastapi import FastAPI, Request
+from fastapi import FastAPI, Request, status
 from fastapi.encoders import jsonable_encoder
 from fastapi.exceptions import RequestValidationError
 from fastapi.responses import JSONResponse
@@ -10,7 +10,7 @@ app = FastAPI()
 @app.exception_handler(RequestValidationError)
 async def validation_exception_handler(request: Request, exc: RequestValidationError):
     return JSONResponse(
-        status_code=422,
+        status_code=status.HTTP_422_UNPROCESSABLE_CONTENT,
         content=jsonable_encoder({"detail": exc.errors(), "body": exc.body}),
     )
 

fastapi/exception_handlers.py

@@ -5,7 +5,7 @@ from fastapi.websockets import WebSocket
 from starlette.exceptions import HTTPException
 from starlette.requests import Request
 from starlette.responses import JSONResponse, Response
-from starlette.status import WS_1008_POLICY_VIOLATION
+from starlette.status import HTTP_422_UNPROCESSABLE_CONTENT, WS_1008_POLICY_VIOLATION
 
 
 async def http_exception_handler(request: Request, exc: HTTPException) -> Response:
@@ -21,7 +21,7 @@ async def request_validation_exception_handler(
     request: Request, exc: RequestValidationError
 ) -> JSONResponse:
     return JSONResponse(
-        status_code=422,
+        status_code=HTTP_422_UNPROCESSABLE_CONTENT,
         content={"detail": jsonable_encoder(exc.errors())},
     )
 

fastapi/openapi/utils.py

@@ -38,6 +38,7 @@ from fastapi.utils import (
 from pydantic import BaseModel
 from starlette.responses import JSONResponse
 from starlette.routing import BaseRoute
+from starlette.status import HTTP_422_UNPROCESSABLE_CONTENT
 
 validation_error_definition = {
     "title": "ValidationError",
@@ -451,7 +452,7 @@ def get_openapi_path(
                     )
                     deep_dict_update(openapi_response, process_response)
                     openapi_response["description"] = description
-            http422 = "422"
+            http422 = str(HTTP_422_UNPROCESSABLE_CONTENT)
             all_route_params = get_flat_params(route.dependant)
             if (all_route_params or route.body_field) and not any(
                 status in operation["responses"]