how to uninstall macport with OS conflict ?

[fx at talgorn.me]

Hello guys!

I want to uninstall macport.
I'm currently running "darwin 16" (OSX Sierra) but my install of port is 
"darwin 15" based.

This means I can not run the port command anymore:
Error: Current platform "darwin 16" does not match expected platform 
"darwin 15"
Error: If you upgraded your OS, please follow the migration 
instructions: https://trac.macports.org/wiki/Migration
OS platform mismatch
     while executing
"mportinit ui_options global_options global_variations"
Error: /opt/local/bin/port: Failed to initialize MacPorts, OS platform 
mismatch

I didn't find usefull instructions for this case at 
https://guide.macports.org/#installing.macports.uninstalling:
"If you need to uninstall MacPorts, and port is functioning, first ...."

But nothing about NOT having port functionning :)

The question is: How can I totally remove macport in this context ?

A huge thank-you!
Fixta.