title: shebang: use interpreter relative to the script path
body: <p>I try to build scripts that work everywhere and always. For this I use a custom-built python, which is always in the parent directory relative to the script.</p>
  
  <p>This way I could load my package on an USB-stick and it would work everywhere, regardless of where the stick is mounted and whether python is installed or not.</p>
  
  <p>However, when I use</p>
  
  <pre><code>#!../python
  </code></pre>
  
  <p>then it works only when the script gets invoked from its directory, which is of course not acceptable.</p>
  
  <p>Is there a way to do this or is this impossible in the current shebang-mechanism?</p>