title: How to customize vim-syntastic?
body: <p>I've written a python script. My vimrc contains:</p>
  
  <pre><code>Plug 'vim-syntastic/syntastic'
  let g:syntastic_python_checkers=['pyflakes']
  </code></pre>
  
  <p>and I'd like to turn this kind of error into warning:</p>
  
  <pre><code>File.py|214 error| local variable 'rank_last_c' is assigned to but never used
  </code></pre>
  
  <p>and my code is like that:</p>
  
  <pre><code>def run():
      ...
      find(something)
      ...
  def find(n):
      ...
  </code></pre>
  
  <p>Clearly, the function 'find(n)' is defined.
  But there's error like that:</p>
  
  <pre><code>File.py|149 error| undefined name 'find'
  </code></pre>
  
  <p>What should I do to customize my syntastic?</p>