title: Error running flake8
body: <p>I recently tried to install Flake8 for Python3 and since then I'm getting the following error message: </p>
  
  <pre><code>/Users/dorsam/.atom/packages/linter/lib/linter-registry.js:159 [Linter] Error running Flake8 Error: /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pycodestyle.py:113: FutureWarning: Possible nested set at position 1
    EXTRANEOUS_WHITESPACE_REGEX = re.compile(r'[[({] | []}),;:]')
      at ChildProcess.&lt;anonymous&gt; (/Users/dorsam/.atom/packages/linter-flake8/node_modules/sb-exec/lib/index.js:56:20)
      at emitTwo (events.js:126:13)
      at ChildProcess.emit (events.js:214:7)
      at maybeClose (internal/child_process.js:925:16)
      at Socket.stream.socket.on (internal/child_process.js:346:11)
      at emitOne (events.js:116:13)
      at Socket.emit (events.js:211:7)
      at Pipe._handle.close [as _onclose] (net.js:554:12)
  </code></pre>