pip安装包错误提示“connection error: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:5...

问题

之前都没什么问题，最近使用pip安装package时，报错提示ssl错误

Collecting fcache
  Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1045)'))': /simple/fcache/
  Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1045)'))': /simple/fcache/
  Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1045)'))': /simple/fcache/
  Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1045)'))': /simple/fcache/
  Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1045)'))': /simple/fcache/
  Could not fetch URL https://pypi.org/simple/fcache/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/fcache/ (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1045)'))) - skipping
  Could not find a version that satisfies the requirement fcache (from versions: )
No matching distribution found for fcache
Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError(SSLCertVerificationError(1, '[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1045)'))) - skipping

解决方法：

1. 重装或更新pip为最新版本（一步到位）

重装：
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py   # 下载安装脚本
sudo python get-pip.py    # 运行安装脚本

更新:
python -m pip install --trusted-host pypi.python.org --trusted-host files.pythonhosted.org --trusted-host pypi.org --upgrade pip

2.携带信任pypi.org域的参数安装 package（每次安装都要补充参数）

# 将  换成你的包名
pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org 

例如
pip install --trusted-host pypi.org --trusted-host files.pythonhosted.org pip setuptools