我正在与Nitrous.IO合作，但在安装VirtualENV并尝试创建虚拟机时，我收到此错误：

Question

action@wanagow-system-124851:~/workspace$ virtualenv -p /usr/bin/python2.7 wanagow                                                          
Traceback (most recent call last):                                                                                                          
  File "/home/action/.parts/bin/virtualenv", line 5, in <module>                                                                            
    from pkg_resources import load_entry_point                                                                                              
  File "/home/action/.parts/packages/python2/2.7.6/lib/python2.7/site-packages/pkg_resources.py", line 2829, in <module>                    
    working_set = WorkingSet._build_master()                                                                                                
  File "/home/action/.parts/packages/python2/2.7.6/lib/python2.7/site-packages/pkg_resources.py", line 451, in _build_master                
    return cls._build_from_requirements(__requires__)                                                                                       
  File "/home/action/.parts/packages/python2/2.7.6/lib/python2.7/site-packages/pkg_resources.py", line 464, in _build_from_requirements     
    dists = ws.resolve(reqs, Environment())                                                                                                 
  File "/home/action/.parts/packages/python2/2.7.6/lib/python2.7/site-packages/pkg_resources.py", line 639, in resolve                      
    raise DistributionNotFound(req)                                                                                                         
pkg_resources.DistributionNotFound: virtualenv==1.11.4                                                                                      
action@wanagow-system-124851:~/workspace$