pip安装mkdocs报错：
[root@postgres02 ~]# pip install mkdoc
WARNING: pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
Collecting mkdoc
WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/mkdoc/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/mkdoc/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/mkdoc/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/mkdoc/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/mkdoc/
Could not fetch URL https://pypi.org/simple/mkdoc/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/mkdoc/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.")) - skipping
ERROR: Could not find a version that satisfies the requirement mkdoc (from versions: none)
ERROR: No matching distribution found for mkdoc
WARNING: You are using pip version 19.2.3, however version 24.0 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
原因：
新版本的pip在安装软件包时用使用https
解决办法：
vim ~/.pip/pip.conf
[global]
index-url = http://mirrors.aliyun.com/pypi/simple/
[install]
trusted-host = mirrors.aliyun.com
或者使用
http://pypi.doubanio.com/simple/
