vk@vk-desktop:~$ virtualenv -p /usr/bin/python3.4 --no-site-packages ~/doc/Python3/virtualenvs/env3.4 
Running virtualenv with interpreter /usr/bin/python3.4
Using base prefix '/usr'
New python executable in /home/vk/doc/Python3/virtualenvs/env3.4/bin/python3.4
Also creating executable in /home/vk/doc/Python3/virtualenvs/env3.4/bin/python
Installing setuptools, pip...done.
vk@vk-desktop:~$ source doc/Python3/virtualenvs/env3.4/bin/activate
(env3.4)vk@vk-desktop:~$ pip install pytest
Requirement already satisfied (use --upgrade to upgrade): pytest in /usr/lib/python2.7/dist-packages
Requirement already satisfied (use --upgrade to upgrade): py>=1.4.19 in /usr/lib/python2.7/dist-packages (from pytest)
Cleaning up...
(env3.4)vk@vk-desktop:~$ python
Python 2.7.6 (default, Jun 22 2015, 17:58:13) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.

virtualenv --python=python3.4 .env

vk@vk-desktop:~/doc/.scripts$ python3.4 -m venv ~/doc/Python3/venv
The virtual environment was not created successfully because ensurepip is not
available.  On Debian/Ubuntu systems, you need to install the python3-venv
package using the following command.
    apt-get install python3-venv
You may need to use sudo with that command.  After installing the python3-venv
package, recreate your virtual environment.
vk@vk-desktop:~/doc/.scripts$ sudo apt-get install python3-venv
[sudo] password for vk: 
Чтение списков пакетов… Готово
Построение дерева зависимостей       
Чтение информации о состоянии… Готово
E: Не удалось найти пакет python3-venv