title: Using pytest when tests are in a separate folder
body: <p>my python folder structure is as follows </p>
  
  <pre><code>repository
    -libraries
       -image
          -imagefuncs.py
       -videos
          -videofuncs.py
       -text
          -textfuncs.py
    -docs
    -tests
       -test_imagefuncs.py
  </code></pre>
  
  <p>For the life of me i cannot figure out how I am supposed to test my functions defined in <code>imagefuncs.py</code> in <code>test_imagefuncs.py</code></p>
  
  <p>I cannot import the libraries folder in test_imagefuncs.py so none of those functions are visible to my testing code. </p>
  
  <p>I'm using python3 and all i want to achieve is do py.test from my root repository folder and have all my tests execute without throwing import errors. </p>
  
  <p>Is modifying the python path the only way to go about achieving this? </p>
  
  <p>I want to achieve this without modifying the system path or python path</p>