HOWTO? Login DSL Modem with Python Requests: need Click "Apply" Button

[snippsat]

you MUST click the "Apply" button in order to actually log in.

Is not so straightforward to figure it out.
onclick="ButtonClick(1)"
ButtonClick(1) is a function/method in JavaScript look at what it dos,
at some point i guess a POST request will be made to a HTTP endpoint.
Tool for inspecting Chrome DevTools,Firefox Developer Tools.
This request is what you most send with Requests to stimulate that button click.

but I couldn't figure out how to get it installed into Linux Mint 17.3.

With Selenium and often in combo with PhantomJS(Selenium can load it).
It easier for there are method click() to click buttons.

Install Selenium it should work with pip. 
The default python3 in Mint17.3 is python3.4.
So sudo pip3 install selenium for using it for Python 3.
python3 my_prog.py to run Python 3.
Linux Python 3 environment
I have a demo with Selenium here.