title: flake8 not showing fatal erros in vscode
body: <p>Vscode is not showing fatal erros in vscode. It is only highlighting warnings in the code. Example:</p>
  
  <p>I have vscode running flake8 from a virtualenv with python 2.7. The settings is as following:</p>
  
  <pre><code>"python.linting.flake8Enabled": true,
  </code></pre>
  
  <p>I'm comparing the results from vscode "problems" window with the results of running flake8 directly from the command line.</p>
  
  <pre class="lang-py prettyprint-override"><code>def foo(bar):
      o += 1
  
      print(bar)
  </code></pre>
  
  <p>When I run flake8 from the command line on the code above, I get all linting errors and warnings,</p>
  
  <pre><code>&gt; flake8 python/mock.py 
  python/mock.py:4:5: F821 undefined name 'o'
  python/mock.py:4:5: F841 local variable 'o' is assigned to but never used
  python/mock.py:5:1: W293 blank line contains whitespace
  </code></pre>
  
  <p>while when I lint this code in vscode, I only getting the warnings.</p>
  
  <pre><code>blank line contains whitespace flake8(W293) [5,1]
  </code></pre>
  
  <p>Am I missing something in the configuration? Is there a way to check how flake8 is being called by vscode?</p>