When I do bench update on my Centos 7 instance I get the following notice in bench.
You are using pip version 6.1.1, however version 7.0.1 is available.
You should consider upgrading via the ‘pip install --upgrade pip’ command.
I updated pip via yum with the following commands from sudo user frappe
./env/bin/pip install --upgrade pip from /frappe-bench/ just worked for me when faced with the warning “You are using pip version 7.0.3, however version 7.1.2 is available.”