$ virtualenv venv --python=python3.5
Running virtualenv with interpreter /usr/bin/python3.5
Using base prefix '/usr'
New python executable in /tmp/sf/venv/bin/python3.5
Also creating executable in /tmp/sf/venv/bin/python
Installing setuptools, pip, wheel...done.
james@sprobox:/tmp/sf$ . venv/bin/activate
(venv) james@sprobox:/tmp/sf$ pip install -U pip
Requirement already up-to-date: pip in ./venv/lib/python3.5/site-packages
(venv) james@sprobox:/tmp/sf$ pip install systemfixtures
Collecting systemfixtures
  Downloading systemfixtures-0.6.5-py2.py3-none-any.whl
Collecting fakesleep (from systemfixtures)
  Downloading fakesleep-0.1.tar.gz
Collecting testtools (from systemfixtures)
  Downloading testtools-2.2.0-py2.py3-none-any.whl (195kB)
    100% |████████████████████████████████| 204kB 2.2MB/s 
Collecting fixtures (from systemfixtures)
  Downloading fixtures-3.0.0-py2.py3-none-any.whl (67kB)
    100% |████████████████████████████████| 71kB 2.3MB/s 
Collecting requests-mock (from systemfixtures)
  Downloading requests_mock-1.3.0-py2.py3-none-any.whl
Collecting pbr (from systemfixtures)
  Downloading pbr-3.0.0-py2.py3-none-any.whl (98kB)
    100% |████████████████████████████████| 102kB 3.0MB/s 
Requirement already satisfied: six in ./venv/lib/python3.5/site-packages (from systemfixtures)
Collecting traceback2 (from testtools->systemfixtures)
  Using cached traceback2-1.4.0-py2.py3-none-any.whl
Collecting python-mimeparse (from testtools->systemfixtures)
  Downloading python_mimeparse-1.6.0-py2.py3-none-any.whl
Collecting unittest2>=1.0.0 (from testtools->systemfixtures)
  Using cached unittest2-1.1.0-py2.py3-none-any.whl
Collecting extras>=1.0.0 (from testtools->systemfixtures)
  Downloading extras-1.0.0-py2.py3-none-any.whl
Collecting requests>=1.1 (from requests-mock->systemfixtures)
  Downloading requests-2.13.0-py2.py3-none-any.whl (584kB)
    100% |████████████████████████████████| 593kB 1.4MB/s 
Collecting linecache2 (from traceback2->testtools->systemfixtures)
  Using cached linecache2-1.0.0-py2.py3-none-any.whl
Collecting argparse (from unittest2>=1.0.0->testtools->systemfixtures)
  Downloading argparse-1.4.0-py2.py3-none-any.whl
Building wheels for collected packages: fakesleep
  Running setup.py bdist_wheel for fakesleep ... done
  Stored in directory: /home/james/.cache/pip/wheels/57/50/c8/c70d45d0f45b1f286669fcaed99a10c85f5fc4e06d647bcb39
Successfully built fakesleep
Installing collected packages: fakesleep, linecache2, traceback2, python-mimeparse, pbr, fixtures, argparse, unittest2, extras, testtools, requests, requests-mock, systemfixtures
Successfully installed argparse-1.4.0 extras-1.0.0 fakesleep-0.1 fixtures-3.0.0 linecache2-1.0.0 pbr-3.0.0 python-mimeparse-1.6.0 requests-2.13.0 requests-mock-1.3.0 systemfixtures-0.6.5 testtools-2.2.0 traceback2-1.4.0 unittest2-1.1.0