title: Git submodule raises import error once used in python project
body: <p>I'm using a git-submodule in my python project.</p>
  
  <p>The submodule project looks like this:</p>
  
  <pre><code>-submodule_project
      - __init__.py
      - debug_util.py
      - parsing_util
          - __init__.py
          - parse.py
          - consts.py
  </code></pre>
  
  <p><code>parse.py</code> imports <code>debug_util.py</code>.
  This structure works fine as the submodule is an independent project.</p>
  
  <p>My project is built like this:</p>
  
  <pre><code>-project
      - __init__.py
      - file1.py
      - some_dir
          - __init__.py
          - main.py
  </code></pre>
  
  <p>So once I use the submodule as a git submodule in my project, the <code>parse.py</code> raises <code>ImportError</code>. This happens once the line which imports the <code>debug_util.py</code> is ran.
  Just to clarify: <code>main.py</code> imports <code>parse.py</code>, which imports <code>debug_util.py</code></p>
  
  <p>Can you explain me what i'm doing wrong, and what are the available solutions to fix this?</p>
  
  <p>Here's my <code>.gitmodules</code> file:</p>
  
  <pre><code>[submodule "submodule_project"]
  path = submodule_project
  url = ../submodule_project.git
  </code></pre>
  
  <p>Thanks in advance for all of you!</p>