ssl.SSLError: tlsv1 alert protocol version

The only thing you have to do is to install requests[security] in your virtualenv. You should not have to use Python 3 (it should work in Python 2.7). Moreover, if you are using a recent version of macOS, you don't have to use homebrew to separately install OpenSSL either.

$ virtualenv --python=/usr/bin/python tempenv  # uses system python
$ . tempenv/bin/activate
$ pip install requests
$ python
>>> import ssl
>>> ssl.OPENSSL_VERSION
'OpenSSL 0.9.8zh 14 Jan 2016'  # this is the built-in openssl
>>> import requests
>>> requests.get('https://api.github.com/users/octocat/orgs')
requests.exceptions.SSLError: HTTPSConnectionPool(host='api.github.com', port=443): Max retries exceeded with url: /users/octocat/orgs (Caused by SSLError(SSLError(1, u'[SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:590)'),))
$ pip install 'requests[security]'
$ python  # install requests[security] and try again
>>> import requests
>>> requests.get('https://api.github.com/users/octocat/orgs')
<Response [200]>

requests[security] allows requests to use the latest version of TLS when negotiating the connection. The built-in openssl on macOS supports TLS v1.2.

Before you install your own version of OpenSSL, ask this question: how is Google Chrome loading https://github.com?

I had the same error and google brought me to this question, so here is what I did, hoping that it helps others in a similar situation.

This is applicable for OS X.

Check in the Terminal which version of OpenSSL I had:

$ python3 -c "import ssl; print(ssl.OPENSSL_VERSION)"
>> OpenSSL 0.9.8zh 14 Jan 2016

As my version of OpenSSL was too old, the accepted answer did not work.

So I had to update OpenSSL. To do this, I updated Python to the latest version (from version 3.5 to version 3.6) with Homebrew, following some of the steps suggested here:

$ brew update
$ brew install openssl
$ brew install python3

Then I was having problems with the PATH and the version of python being used, so I just created a new virtualenv making sure that the newest version of python was taken:

$ virtualenv webapp --python=python3.6

Issue solved.