pip2 安装包踩坑

报错：
DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support pip 21.0 will remove support for this functionality.
WARNING: Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:727)'),)': /simple/dateutil/
WARNING: Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:727)'),)': /simple/dateutil/
WARNING: Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:727)'),)': /simple/dateutil/
WARNING: Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:727)'),)': /simple/dateutil/
WARNING: Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:727)'),)': /simple/dateutil/
Could not fetch URL https://pypi.org/simple/dateutil/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/dateutil/ (Caused by SSLError(SSLEOFError(8, u'EOF occurred in violation of protocol (_ssl.c:727)'),)) - skipping
ERROR: Could not find a version that satisfies the requirement dateutil (from versions: none)
ERROR: No matching distribution found for dateutil

pip2 install sklearn -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com

解决来源：
https://blog.csdn.net/weixin_43943548/article/details/103035458?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-2.control&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromBaidu-2.control