- 客户端没有执行操作的权限
- 客户端没有访问资源的权限
- 客户端要访问的项目不存在
- 等等 ...

遇到这些情况时，通常要返回 **4XX**（400 至 499）**HTTP 状态码**。

**4XX** 状态码与表示请求成功的 **2XX**（200 至 299） HTTP 状态码类似。

只不过，**4XX** 状态码表示客户端发生的错误。

大家都知道**「404 Not Found」**错误，还有调侃这个错误的笑话吧？

## 使用 `HTTPException`

向客户端返回 HTTP 错误响应，可以使用 `HTTPException`。

### 导入 `HTTPException`

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

```

	LatestModTime time.Time `msg:"lm"`

	Versions     []FileInfo `msg:"vs"`
	FreeVersions []FileInfo `msg:"fvs"`
}

// findVersionIndex will return the version index where the version
// was found. Returns -1 if not found.
func (f *FileInfoVersions) findVersionIndex(v string) int {
	if f == nil || v == "" {
		return -1
	}
	if v == nullVersionID {
		for i, ver := range f.Versions {
			if ver.VersionID == "" {

			update, err := testCase.meta.validate(testCase.pools)
			if testCase.expectedErr {
				t.Log(err)
			}
			if err != nil && !testCase.expectedErr {
				t.Errorf("Expected success, but found %s", err)
			}
			if err == nil && testCase.expectedErr {
				t.Error("Expected error, but got `nil`")
			}
			if update != testCase.expectedUpdate {

				return
			}
		default:
			bts, err = msgp.Skip(bts)
			if err != nil {
				err = msgp.WrapError(err)
				return
			}
		}
	}
	o = bts
	return
}

// Msgsize returns an upper bound estimate of the number of bytes occupied by the serialized message
func (z RStat) Msgsize() (s int) {
	s = 1 + 6 + msgp.Int64Size + 6 + msgp.Int64Size
	return
}

// DecodeMsg implements msgp.Decodable

MINIO_OLD=("$PWD/minio.RELEASE.2020-10-28T08-16-50Z" --config-dir "$MINIO_CONFIG_DIR" server)
MINIO=("$PWD/minio" --config-dir "$MINIO_CONFIG_DIR" server)

if [ ! -x "$PWD/minio" ]; then
	echo "minio executable binary not found in current directory"
	exit 1
fi

function download_old_release() {
	if [ ! -f minio.RELEASE.2020-10-28T08-16-50Z ]; then

Setting CC is not necessary if the toolchain is built with CC_FOR_TARGET set.

To use the go tool to run individual programs and tests, put $GOROOT/bin into PATH to ensure
the go_ios_$GOARCH_exec wrapper is found. For example, to run the archive/tar tests:

	export PATH=$GOROOT/bin:$PATH
	GOOS=ios GOARCH=amd64 CGO_ENABLED=1 go test archive/tar

The go_ios_exec wrapper uses GOARCH to select the emulator (amd64) or the device (arm64).

// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

TEXT errors(SB),$0
	MOV	$errors(SB), (X5)		// ERROR "address load must target register"
	MOV	$8(SP), (X5)			// ERROR "address load must target register"
	MOVB	$8(SP), X5			// ERROR "unsupported address load"
	MOVH	$8(SP), X5			// ERROR "unsupported address load"

						duration = time.Duration(val) * time.Millisecond
					case ts.Unit.IsSetMICROS():
						duration = time.Duration(val) * time.Microsecond
					default:
						return nil, errors.New("Invalid LogicalType annotation found")
					}
					value = sql.FormatSQLTimestamp(time.Unix(0, 0).Add(duration))
				}
			} else if se.GetConvertedType() == parquettypes.ConvertedType_TIMESTAMP_MILLIS {
				duration := time.Duration(val) * time.Millisecond

// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

#include "../../../../../runtime/textflag.h"

TEXT	foo(SB), DUPOK|NOSPLIT, $0

	ADDF	F0, F1, F2    // 002a31ee
	ADDD.EQ	F3, F4, F5    // 035b340e
	ADDF.NE	F0, F2        // 002a321e
	ADDD	F3, F5        // 035b35ee
	SUBF	F0, F1, F2    // 402a31ee
	SUBD.EQ	F3, F4, F5    // 435b340e

// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// The linkcheck command finds missing links in the godoc website.
// It crawls a URL recursively and notes URLs and URL fragments
// that it's seen and prints a report of missing links at the end.
package main

import (
	"errors"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"