初探Scrapy 时，也不知道按照哪里的文档装的，由于安装低版本的pyasn1 后，使用pip uninstall 都 卸不了
步骤如下：
异常：
pyasn1-modules 0.2.1 has requirement pyasn1<0.5.0,>=0.4.1, but you'll have pyasn1 0.1.7 which is incompatible.
网上方案：
https://blog.csdn.net/ksx_120999/article/details/80012650
pip install pyasn1-modules
报错
Cannot uninstall 'pyasn1'. It is a distutils installed project and thus we cannot accurately determine which files belong to it which would lead to only a partial uninstall.
貌似重新安装是先uninstall 然后，卸不了
于是从 pyasn1 官网下源代码再安装
https://pypi.org/project/pyasn1/#files 官网地址
下载
下载后，解压，进入根目录
python setup.py build
python setup.py install
OK，pyasn1 己安装指定版本。