Return non zero code on failure

run_tests.py

 #!/usr/bin/env python
+import sys
 import unittest
 
-#Run all tests
-if __name__ == '__main__':
+
+# Run all tests
+def main(args=None):
     test_loader = unittest.TestLoader()
     test_suite = test_loader.discover('tests', pattern='test_*.py')
     runner = unittest.TextTestRunner()
-    runner.run(test_suite)
+    results = runner.run(test_suite)
+    return results.wasSuccessful()
+
+
+if __name__ == '__main__':
+    sys.exit(0 if main(sys.argv[1:]) else 1)