无法获取URLhttps://pypi.python.org/simple/xlrd/

当我尝试在cmd中运行这个命令pip install xlrd时，我在中遇到了这个错误。我以提升的权限使用cmd，但仍然无效。请帮忙。多谢各位

全部错误：

C:\Users\Rodne>pip install xlrd
Collecting xlrd
  Could not fetch URL https://pypi.python.org/simple/xlrd/: There was a problem confirming the ssl certificate: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749) - skipping
  Could not find a version that satisfies the requirement xlrd (from versions: )
No matching distribution found for xlrd
You are using pip version 9.0.1, however version 18.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

我有python 3.6

我尝试升级，结果是：

C:\WINDOWS\system32>pip install pip setuptools --upgrade
Could not fetch URL https://pypi.python.org/simple/pip/: There was a problem confirming the ssl certificate: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749) - skipping
Requirement already up-to-date: pip in c:\users\rodne\appdata\local\programs\python\python36\lib\site-packages
Could not fetch URL https://pypi.python.org/simple/setuptools/: There was a problem confirming the ssl certificate: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749) - skipping
Requirement already up-to-date: setuptools in c:\users\rodne\appdata\local\programs\python\python36\lib\site-packages
You are using pip version 9.0.1, however version 18.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

使用受信任的安装为我提供了以下功能：

C:\WINDOWS\system32>pip install --trusted-host pypi.python.org xlrd
Collecting xlrd
  Could not fetch URL https://pypi.python.org/simple/xlrd/: There was a problem confirming the ssl certificate: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749) - skipping
  Could not find a version that satisfies the requirement xlrd (from versions: )
No matching distribution found for xlrd
You are using pip version 9.0.1, however version 18.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

您可以使pypi.python.org、pypi.org和files.pythonhosted.org成为受信任的主机，以绕过SSL证书验证问题：

pip install --trusted-host=pypi.python.org --trusted-host=pypi.org --trusted-host=files.pythonhosted.org xlrd

还可以使用上面的命令安装-升级pip：所有三个受信任的主机条目。