Had exactly the same problem using Ubuntu 16.04. LTS Exact same error messages.
I tried to update python manually, tried to update pip, tried the 'sudo -H' ... nothing worked.
When I upgraded to Ubuntu 18.04. LTS the installation of Electrum 3.3.2 went smooth and without a problem. Probably it's the same problem in mint, the python version is outdated.
What mint version are you using?
Upgrade if possible.
Is it python3 and pip3 you've been trying to update also and not just regular python?
As said, look at abdusammads post too.