缓存更新错误

Question

我无法从 Ubuntu 软件中心下载许多软件。它显示一条错误信息： “无法解析软件包依赖关系” 由于我是新用户，所以我搜索了解决方案，其中说将软件和更新中的下载来源选项从“服务器”更改为“国家/地区”到“主服务器”，然后安装更新会有所帮助。但这样做时出现了这个错误 - 弹出一个屏幕说无法下载存储库信息重新加载后。当我查看详细信息时，它显示以下错误- E：GPG 错误：https://private-ppa.launchpad.net可信版本：以下签名无效：NODATA 2。

请回答这个问题，并且请求不要将该问题标记为重复，因为之前的答案对我没有帮助。

请帮忙。提前致谢。

from flask import Flask, render_template, request, jsonify, url_for, redirect
from flask_cors import CORS, cross_origin
import subprocess

mediaConnect = Flask(__name__)
CORS(mediaConnect, support_credentials = True)

@mediaConnect.route('/listFlows', methods = ['GET', 'POST'])
@cross_origin(origin = '*', headers = ['Content-Type', 'Authorization'], support_credentials = True)
def listFlows():
    if(request.method == 'POST'):
        userInput = request.get_json()

        command = 'aws mediaconnect list-flows --region ' + userInput['region']
        pipe = subprocess.Popen(command, shell = True, stdout = subprocess.PIPE, stderr = subprocess.STDOUT)
        stdout = pipe.communicate()

        return stdout

@mediaConnect.route('/createFlow', methods = ['GET', 'POST'])
@cross_origin(origin = '*', headers = ['Content-Type', 'Authorization'], support_credentials = True)
def createFlow():
    if(request.method == 'POST'):
        userInput = request.get_json()

        command = 'aws mediaconnect create-flow --region ' + userInput['region'] + ' --availability-zone ' + userInput['az'] + ' --name ' + userInput['name'] + ' --source Description="' + userInput['description'] + ',IngestPort=' + userInput['ingestPort'] + ',Name=' + userInput['sourceName'] + ',Protocol=' + userInput['protocol'] + ',WhitelistCidr=' + userInput['whitelistCidr']
        pipe = subprocess.Popen(command, shell = True, stdout = subprocess.PIPE, stderr = subprocess.STDOUT)
        stdout = pipe.communicate()

        return stdout

@mediaConnect.route('/describeFlow', methods = ['GET', 'POST'])
@cross_origin(origin = '*', headers = ['Content-Type', 'Authorization'], support_credentials = True)
def describeFlow():
    if(request.method == 'POST'):
        userInput = request.get_json()

        command = 'aws mediaconnect describe-flow --region ' + userInput['region'] + ' --flow-arn ' + userInput['flowArn']
        pipe = subprocess.Popen(command, shell = True, stdout = subprocess.PIPE, stderr = subprocess.STDOUT)
        stdout = pipe.communicate()

        return stdout

@mediaConnect.route('/deleteFlow', methods = ['GET', 'POST'])
@cross_origin(origin = '*', headers = ['Content-Type', 'Authorization'], support_credentials = True)
def deleteFlow():
    if(request.method == 'POST'):
        userInput = request.get_json()

        command = 'aws mediaconnect delete-flow --region ' + userInput['region'] + ' --flow-arn ' + userInput['flowArn']
        pipe = subprocess.Popen(command, shell = True, stdout = subprocess.PIPE, stderr = subprocess.STDOUT)
        stdout = pipe.communicate()

        return stdout

if __name__ == '__main__':
    mediaConnect.run(debug = True)