我也解决不了，所以直接在urllib的扩展那里加了个删除直接强制修改

 

\Python\Python39\Lib\urllib\request.py

1330行左右在　　

headers["Connection"] = "close"
headers = {name.title(): val for name, val in headers.items()}

的下面加上自己想小写的那一部分，例如我想把uuid小写就是这样写的：

headers["Connection"] = "close"
headers = {name.title(): val for name, val in headers.items()}

if headers['Uuid'] is not None:

    headers['uuid']=headers['Uuid']
    del headers['Uuid']