pip issue installing almost any library

I found it sufficient to specify the pypi host as trusted. Example:

pip install --trusted-host pypi.python.org pytest-xdistpip install --trusted-host pypi.python.org --upgrade pip

This solved the following error:

  Could not fetch URL https://pypi.python.org/simple/pytest-cov/: There was a problem confirming the ssl certificate: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:600) - skipping  Could not find a version that satisfies the requirement pytest-cov (from versions: )No matching distribution found for pytest-cov

Update April 2018:To anyone getting the TLSV1_ALERT_PROTOCOL_VERSION error: it has nothing to do with trusted-host/verification issue of the OP or this answer. Rather the TLSV1 error is because your interpreter does not support TLS v1.2, you must upgrade your interpreter. See for example https://news.ycombinator.com/item?id=13539034, http://pyfound.blogspot.ca/2017/01/time-to-upgrade-your-python-tls-v12.html and https://bugs.python.org/issue17128.

Update Feb 2019:For some it may be sufficient to upgrade pip. If the above error prevents you from doing this, use get-pip.py. E.g. on Linux,

curl https://bootstrap.pypa.io/get-pip.pysudo python get-pip.py

More details at https://pip.pypa.io/en/stable/installing/.

I used pip version 9.0.1 and had the same issue, all the answers above didn't solve the problem, and I couldn't install python / pip with brew for other reasons.

Upgrading pip to 9.0.3 solved the problem. And because I couldn't upgrade pip with pip I downloaded the source and installed it manually.

1. Download the correct version of pip from - https://pypi.org/simple/pip/
2. sudo python3 pip-9.0.3.tar.gz - Install pip

Or you can install newer pip with:

curl https://bootstrap.pypa.io/get-pip.py | python

Pypi removed support for TLS versions less than 1.2

You need to re-install Pip, do

curl https://bootstrap.pypa.io/get-pip.py | python

or for global Python:

curl https://bootstrap.pypa.io/get-pip.py | sudo python