setup_virtualenv.py fails on el7

[dennybaa]

  File "/usr/share/python/st2actions/lib/python2.7/site-packages/virtualenv.py", line 1192, in install_python
    copy_required_modules(home_dir, symlink)
  File "/usr/share/python/st2actions/lib/python2.7/site-packages/virtualenv.py", line 1131, in copy_required_modules
    copyfile(filename, dst_filename, symlink)
  File "/usr/share/python/st2actions/lib/python2.7/site-packages/virtualenv.py", line 468, in copyfile
    os.makedirs(os.path.dirname(dest))
  File "/usr/share/python/st2actions/lib64/python2.7/os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 2] No such file or directory: '/opt/stackstorm/virtualenvs/github/lib64/python2.7'

related #53

[dennybaa]

leaving it so far until tested