title: python - unittest - ImportError: Start directory is not importable
body: <p>I'm following python unittest to make some test and use discover function to pack tests to a suite.
  However when I try to run the test with unittest, I get this error:</p>
  
  <pre><code>Traceback (most recent call last):
     File "D:/Project/run_tests.py", line 12, in &lt;module&gt;
       suite2 = unittest.defaultTestLoader.discover(dir2, pattern='test*.py')
     File "C:\Python\Python36-32\lib\unittest\loader.py", line 338, in discover
       raise ImportError('Start directory is not importable: %r' % start_dir)
  ImportError: Start directory is not importable: 'D:\\Project\\dir2'
  </code></pre>
  
  <p>This is how the run_tests.py looks like:</p>
  
  <pre><code>import unittest
  
  if __name__ == "__main__":
  
      dir1 = "./test1"
      suite1 = unittest.defaultTestLoader.discover(dir1, pattern='test*.py')
      runner1 = unittest.TextTestRunner()
      runner1.run(suite1)
  
  
      dir2 = "./tes2"
      suite2 = unittest.defaultTestLoader.discover(dir2, pattern='test*.py')
      runner2 = unittest.TextTestRunner()
      runner2.run(suite2)
  </code></pre>