PIP question... Requirement already up-to-date

During the upgrade process of Home Assistant PIP tells me…

You are using pip version 8.1.1, however version 9.0.1 is available
You should consider upgrading via the 'pip install --upgrade pip' command.

… but when I try to upgrade I get this message…

Requirement already up-to-date: pip in ./.local/lib/python3.5/site-packages

… well… PIP need to be updated or not?

The command pip -V tell me that PIP is already updated…

pip 9.0.1 from /home/igor/.local/lib/python3.5/site-packages (python 3.5)

Why PIP have this (apparent) conflict?