title: A test running with nosetests fails with ImportError, but works with python command
body: <p>When run a test with <code>python mycore/tests4extractor.py</code> it works. If run the test with  <code>nosetests ./mycore/tests4extractor.py</code> it fails with <code>ImportError: No module named extractor</code>. I am in the <code>helpers</code> folder.</p>
  
  <p>The project structure is:</p>
  
  <pre><code>helpers/
      mycore/
          __init__.py
          extractor.py
          tests4extractor.py
  </code></pre>
  
  <p>Setting PYTHONPATH to the absolute path to <code>helpers</code> and/or <code>helpers/mycore</code> doesn't help.</p>
  
  <p><strong>Answer</strong></p>
  
  <p>tests4extractor.py:</p>
  
  <pre><code>    import mycore
      from extractor import extract
  </code></pre>
  
  <p>should be changed to:</p>
  
  <pre><code>    import mycore
      from mycore.extractor import extract
  </code></pre>
  
  <p>And python should be run with <code>python -mmycore.tests4_strings</code></p>