title: Difficulty including the extra intellisense paths in the python linter's scope
body: <p>I am working with ros on ubuntu 16.04. Because of this I am working with a virtual environment for python 2.7 and the ros python modules (rospy for example). The "python.pythonPath" is set to the virtual environment and the ros modules are linked through "python.autoComplete.extraPaths".</p>
  
  <p>This leads to the issue where the python linter raises an error for import rospy claiming that it can not import it. However, the python intellisense is still able detect and help with the rospy module (which makes sense due to the python.autoComplete.extraPaths setting). </p>
  
  <p>Is there a way to include the extra paths for autoComplete for the linter as well? At this point, no longer including the virtual environment for the python path is not a desirable option so I am looking for a way to have the linter include the extra paths for ros python modules and the modules in the virtual environment.</p>