Unable to pip install package on Mac after first deployment

## Location within the Course

* Section: 3
* Lesson: 7
* Language: English

## Description

After deploying successfully to PyPI, I was unable to pip install it into a new `test-env`. Here is the error:
```
Download error on https://pypi.python.org/simple/pytest-runner/:
[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:748) -- Some packages may not be found!
Couldn't find index page for 'pytest-runner' (maybe misspelled?)
Download error on https://pypi.python.org/simple/: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:748) -- Some packages may not be found!
No local packages or working download links found for pytest-runner
```
### Things I tried that didn't work
Based upon https://stackoverflow.com/questions/25981703/pip-install-fails-with-connection-error-ssl-certificate-verify-failed-certi/46410817#46410817
I added `$HOME/Library/Application Support/pip/pip.conf` file with:
```
[global]
trusted-host = pypi.python.org
```
That did not work. So I went to: https://github.com/pypa/pip/issues/4205
I tried `pip install --trusted-host pypi.python.org pip --upgrade`; that did not help. Also did `pip install incremental` that made no apparent difference.

### What worked
The previous pypa issue above referenced this issue: https://github.com/heroku/heroku-django-template/issues/79
where I found the instruction to run `/Applications/Python\ 3.6/Install\ Certificates.command`, after which things were OK.

Maybe this can be put into an FAQ if others have this problem. Should include links to the issues since a number of people indicated that other things fixed the similar error on their machines.