My pip version was off -- every pip command was saying:

```
You are using pip version 6.0.8, however version 8.1.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

```

And I didn't like the answers given here: [How can I get rid of this warning to upgrade from pip?](https://stackoverflow.com/questions/36410756/how-can-i-get-rid-of-this-warning-to-upgrade-from-pip) because they all want to get `pip` out of sync with the RH version.

So I tried a clean system install with this VagrantFile:

```
Vagrant.configure("2") do |config|

  config.ssh.username   = 'root'
  config.ssh.password   = 'vagrant'
  config.ssh.insert_key = 'true'

  config.vm.box = "bento/centos-7.3"

  config.vm.provider "virtualbox" do |vb|
    vb.cpus   = "4"
    vb.memory = "2048"
  end

  config.vm.synced_folder "..", "/vagrant"

  config.vm.network "public_network", bridge: "eth0", ip: "192.168.1.31"

  config.vm.provision "shell", inline: <<-SHELL
    set -x

    # Install pip
    yum install -y epel-release
    yum install -y python-pip
    pip freeze   # See if pip prints version warning on fresh OS install.

  SHELL

end

```

But then I got:

```
==> default: ++ pip freeze
==> default: You are using pip version 8.1.2, however version 9.0.1 is available.
==> default: You should consider upgrading via the 'pip install --upgrade pip' command.

```

So it seems that I'm using the wrong commands to install `pip`. What are correct commands to use?