使用pip报错：Could not fetch URL http

** WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by ‘NewConnectionError(’<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7fcef6598280>: Failed to establish a new connection: [Errno -2] Name or service not known’)’: /simple/schedule/
** WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by ‘NewConnectionError(’<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7fcef6598e20>: Failed to establish a new connection: [Errno -2] Name or service not known’)’: /simple/schedule/
** WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by ‘NewConnectionError(’<pip._vendor.urllib3.connection.HTTPSConnection object at 0x7fcef6598fd0>: Failed to establish a new connection: [Errno -2] Name or service not known’)’: /simple/schedule/
** WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by ‘SSLError(SSLCertVerificationError(1, ‘[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1129)’))’: /simple/schedule/
** WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by ‘SSLError(SSLCertVerificationError(1, ‘[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: self signed certificate in certificate chain (_ssl.c:1129)’))’: /simple/schedule/

解决办法

pip install 要安装的包名 -i http://pypi.douban.com/simple --trusted-host pypi.douban.com

#例如：
pip install requests -i http://pypi.douban.com/simple --trusted-host pypi.douban.com

常用镜像源：
1、阿里云：http://mirrors.aliyun.com/pypi/simple/
2、中国科技大学： https://pypi.mirrors.ustc.edu.cn/simple/
3、豆瓣： http://pypi.douban.com/simple/
4、清华大学：https://pypi.tuna.tsinghua.edu.cn/simple/
5、中国科学技术大学：http://pypi.mirrors.ustc.edu.cn/simple/