title: Test discovery failure when tests in different directories are called the same
body: <p>Using py.test, two tests called the same in different directory causes py.test to fail. Why is that? How can I change this without renaming all the tests?</p>
  
  <p>To duplicate do:</p>
  
  <pre><code>; cd /var/tmp/my_test_module
  ; mkdir -p ook/test           
  ; mkdir -p eek/test
  ; touch ook/test/test_proxy.py
  ; touch eek/test/test_proxy.py
  ; py.test
  ============================= test session starts ==============================
  platform linux2 -- Python 2.7.3 -- pytest-2.2.4
  collected 0 items / 1 errors 
  
  ==================================== ERRORS ====================================
  ___________________ ERROR collecting ook/test/test_proxy.py ____________________
  import file mismatch:
  imported module 'test_proxy' has this __file__ attribute:
    /home/ygolanski/code/junk/python/mymodule/eek/test/test_proxy.py
  which is not the same as the test file we want to collect:
    /home/ygolanski/code/junk/python/mymodule/ook/test/test_proxy.py
  HINT: remove __pycache__ / .pyc files and/or use a unique basename for your test file modules
  =========================== 1 error in 0.01 seconds ============================
  </code></pre>