title: Make import work executed from different path
body: <p>Imagine having this structure</p>
  <pre><code>my_run
  ./dir_a:
      __init__.py
      a.py
  ./dir_b:
      __init__.py
      b.py
  ./dir_c
      __init__.py
      c.py
  </code></pre>
  <p>a.py containing from dir_b import b</p>
  <p>b.py containing from dir_c import c</p>
  <p>Is there a way to be able to execute my_run (symlink to a.py) without changing import path by ..dir_ ?</p>