VirutalEnv

sudo pip install --upgrade pip virtualenv setuptools

The directory '/home/adolfo/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/adolfo/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.

install pip for python 3 in ubuntu 18.04

$ sudo apt-get update
$ sudo apt-get upgrade
$ sudo apt-get install libssl-dev openssl libreadline-dev
$ cd ~
$ wget https://www.python.org/ftp/python/3.6.1/Python-3.6.1.tgz
$ tar zxf Python-3.6.1.tgz
$ cd Python-3.6.1
$ ./configure
$ make
$ sudo make install