pip install fails with "connection error: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:598)"

I am very new to Python and trying to > pip install linkchecker on Windows 7. Some notes:

• pip install is failing no matter the package. For example, > pip install scrapy also results in the SSL error.
• Vanilla install of Python 3.4.1 included pip 1.5.6. The first thing I tried to do was install linkchecker. Python 2.7 was already installed, it came with ArcGIS. python and pip were not available from the command line until I installed 3.4.1.
• > pip search linkchecker works. Perhaps that is because pip search does not verify the site's SSL certificate.
• I am in a company network but we do not go through a proxy to reach the Internet.
• Each company computer (including mine) has a Trusted Root Certificate Authority that is used for various reasons including enabling monitoring TLS traffic to https://google.com. Not sure if that has anything to do with it.

Here are the contents of my pip.log after running pip install linkchecker:

Downloading/unpacking linkchecker
  Getting page https://pypi.python.org/simple/linkchecker/
  Could not fetch URL https://pypi.python.org/simple/linkchecker/: connection error: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:598)
  Will skip URL https://pypi.python.org/simple/linkchecker/ when looking for download links for linkchecker
  Getting page https://pypi.python.org/simple/
  Could not fetch URL https://pypi.python.org/simple/: connection error: HTTPSConnectionPool(host='pypi.python.org', port=443): Max retries exceeded with url: /simple/ (Caused by <class 'http.client.CannotSendRequest'>: Request-sent)
  Will skip URL https://pypi.python.org/simple/ when looking for download links for linkchecker
  Cannot fetch index base URL https://pypi.python.org/simple/
  URLs to search for versions for linkchecker:
  * https://pypi.python.org/simple/linkchecker/
  Getting page https://pypi.python.org/simple/linkchecker/
  Could not fetch URL https://pypi.python.org/simple/linkchecker/: connection error: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:598)
  Will skip URL https://pypi.python.org/simple/linkchecker/ when looking for download links for linkchecker
  Could not find any downloads that satisfy the requirement linkchecker
Cleaning up...
  Removing temporary dir C:\Users\jcook\AppData\Local\Temp\pip_build_jcook...
No distributions at all found for linkchecker
Exception information:
Traceback (most recent call last):
  File "C:\Python34\lib\site-packages\pip\basecommand.py", line 122, in main
    status = self.run(options, args)
  File "C:\Python34\lib\site-packages\pip\commands\install.py", line 278, in run
    requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundle=self.bundle)
  File "C:\Python34\lib\site-packages\pip\req.py", line 1177, in prepare_files
    url = finder.find_requirement(req_to_install, upgrade=self.upgrade)
  File "C:\Python34\lib\site-packages\pip\index.py", line 277, in find_requirement
    raise DistributionNotFound('No distributions at all found for %s' % req)
pip.exceptions.DistributionNotFound: No distributions at all found for linkchecker

pip install gensim config --global http.sslVerify false

Just install any package with the "config --global http.sslVerify false" statement

You can ignore SSL errors by setting pypi.org and files.pythonhosted.org as well as the older pypi.python.org as trusted hosts.

$ pip install --trusted-host pypi.org --trusted-host pypi.python.org --trusted-host files.pythonhosted.org <package_name>

Note: Sometime during April 2018, the Python Package Index was migrated from pypi.python.org to pypi.org. This means "trusted-host" commands using the old domain no longer work, but you can add both.

Permanent Fix

Since the release of pip 10.0, you should be able to fix this permanently just by upgrading pip itself:

$ pip install --trusted-host pypi.org --trusted-host pypi.python.org --trusted-host files.pythonhosted.org pip setuptools

Or by just reinstalling it to get the latest version:

$ curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py

(… and then running get-pip.py with the relevant Python interpreter).

pip install <otherpackage> should just work after this. If not, then you will need to do more, as explained below.

You may want to add the trusted hosts and proxy to your config file.

pip.ini (Windows) or pip.conf (unix)

[global]
trusted-host = pypi.python.org
               pypi.org
               files.pythonhosted.org

Alternate Solutions (Less secure)

Most of the answers could pose a security issue.

Two of the workarounds that help in installing most of the python packages with ease would be:

• Using easy_install: if you are really lazy and don't want to waste much time, use easy_install <package_name>. Note that some packages won't be found or will give small errors.
• Using Wheel: download the Wheel of the python package and use the pip command pip install wheel_package_name.whl to install the package.

You can specify a cert with this param:

pip --cert /etc/ssl/certs/FOO_Root_CA.pem install linkchecker

See: Docs » Reference Guide » pip

If specifying your company's root cert doesn't work maybe the cURL one will work: http://curl.haxx.se/ca/cacert.pem

You must use a PEM file and not a CRT file. If you have a CRT file you will need to convert the file to PEM There are reports in the comments that this now works with a CRT file but I have not verified.

Also check: SSL Cert Verification.

For me the problem was fixed by creating a folder pip, with a file: pip.ini in C:\Users\<username>\AppData\Roaming\ e.g:

C:\Users\<username>\AppData\Roaming\pip\pip.ini

Inside it I wrote:

[global]
trusted-host = pypi.python.org
               pypi.org
               files.pythonhosted.org

I restarted python, and then pip permanently trusted these sites, and used them to download packages from.

If you can't find the AppData Folder on windows, write %appdata% in file explorer and it should appear.