title: What is const char* for Python3
body: <p>A function in C is as following:</p>
  
  <pre><code>char* test(const char* input, size_t length);
  </code></pre>
  
  <p>use swig(3.0.2) to export to python extension.</p>
  
  <p>In python2, run <code>test("hello",len("hello"))</code>, the function works quite well.</p>
  
  <p>But in python 3, run <code>config="hello";test(config.encode("utf-8"),len(config.encode("utf-8")))</code></p>
  
  <pre><code>TypeError: in method 'test', argument 0 of type 'char const *'
  </code></pre>
  
  <p>How can I use this function in Python3?</p>