title: [mitmproxy]How does mitmproxy7 detect proxy failure?
body: <p>How does mitmproxy7 detect proxy failure? Catch the exception and fix it</p>
  <pre><code>127.0.0.1:5297: error establishing server connection: [Errno 10061] Connect call failed ('127.0.0.1', 8089)
  </code></pre>
  <p><a href="https://i.stack.imgur.com/qtRpH.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qtRpH.png" alt="enter image description here" /></a></p>