Ошибка при установке Raspberry OpenCV

pi@raspberrypi:~ $ mkvirtualenv cv
Using base prefix '/usr'
Traceback (most recent call last):
  File "/usr/local/bin/virtualenv", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.5/dist-packages/virtualenv.py", line 712, in main
    symlink=options.symlink)
  File "/usr/local/lib/python3.5/dist-packages/virtualenv.py", line 927, in create_environment
    site_packages=site_packages, clear=clear, symlink=symlink))
  File "/usr/local/lib/python3.5/dist-packages/virtualenv.py", line 1112, in install_python
    mkdir(lib_dir)
  File "/usr/local/lib/python3.5/dist-packages/virtualenv.py", line 324, in mkdir
    os.makedirs(path)
  File "/usr/lib/python3.5/os.py", line 231, in makedirs
    makedirs(head, mode, exist_ok)
  File "/usr/lib/python3.5/os.py", line 231, in makedirs
    makedirs(head, mode, exist_ok)
  File "/usr/lib/python3.5/os.py", line 241, in makedirs
    mkdir(name, mode)
PermissionError: [Errno 13] Permission denied: '/cv'