How do I upgrade bootstrap in my mezzanine's project?
This might break your things all the classes which are obsoleted will not work in newer version to get prevent this refactor all view files . Simple Solution is change the file in  static/ and import the partials header or footer file linked
Environments
pc: mac os 10.13.1
Versions
python: 3.6.2
mezzanine: 4.3.1
django: 1.11.16
bootstrap: 3.3.5  (confirmed in /{my_name}/anaconda3/lib/python3.6/site-packages/mezzanine/core/static/css/bootstrap.css)

Here, my mezzanine project has base.html for site interface. There is the code to get the css-code(design). That is bootstrap.css.
But the bootstrap.css relies to bootstrap3(3.3.5), and I have to use bootstrap4(4.0.0). (This is my boss's order.)
Then, I wanna get(download) bootstrap4, put it to right directory and change bootstrap dependency by linking to the directory which I put earlier.
How should I achieve it?