title: subprocess - FileNotFoundError when shell=False
body: <p>I'm making a GUI that can execute on the command prompt using subprocess and tkinter. </p>
  
  <pre><code>    def test_subprocess(self):
          proc = subprocess.Popen(["echo", "Hello"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, universal_newlines=True, shell=False)
          response = proc.communicate()[0]
          self.log.insert("end", response)
  </code></pre>
  
  <p>If I set <code>shell=False</code>, I get this error:</p>
  
  <pre><code>FileNotFoundError: [WinError 2] The system cannot find the file specified
  </code></pre>
  
  <p>I already have the arguments separated into a sequence.</p>