The command is working fine, it's just letting you know that you should use a virtual environment. Parts of the operating system use Python too so if you change the versions or install random stuff to environment that the operating system uses you could break the whole VPS.
Here is a guide for how to create a virtual environment and install modules with pip inside it. https://packaging.python.org/en/latest/guides/installing-using-pip-and-virtual-environments/