The Tsinghua source (tsinghua) for PIP is not working, and it is also not possible to switch to other sources.（PIP的清华源（tsinghua）无法使用，并且无法切换其他源） #226
Description
In China, QPython defaults to using the Tsinghua source (tsinghua), but the Tsinghua source is returning a 403 error. The following methods have been tried but still fail to switch the source. What can be done to resolve this?
1、Using the command pip install <package_name> --index-url https://pypi.org/simple is ineffective; it still uses the Tsinghua source.
2、After resetting with pip config unset global.index-url and then setting it again with pip config set global.index-url https://pypi.org/simple, the command pip config list shows that global.index-url='https://pypi.org/simple'. However, it is still ineffective, and the Tsinghua source is still being used.
在中国，Qpython默认使用清华源（tsinghua），但是清华源出现403错误。通过以下办法依旧无法更换源，请问如何解决？
1.通过 pip install <package_name> --index-url https://pypi.org/simple，无效，依旧使用清华源。
2.通过pip config unset global.index-url重置后，通过pip config set global.index-url https://pypi.org/simple设置，此时使用pip config list显示global.index-url='https://pypi.org/simple。但依旧无效，依旧使用清华源。