Add check for Python 3.5+ in test script

test.py

@@ -44,11 +44,17 @@ def run_tests(tests):
 
 
 def main():
+    if sys.version_info < (3, 5):  # We use features introduced in Python 3.5
+        sys.stderr.write('{}: Python 3.5 or later is needed for this script\n'
+                         .format(__file__))
+        return 1
+
     tests = ['lint']  # Only tests that are always safe and meaningful to run
     if len(sys.argv) > 1:
         tests = sys.argv[1:]
 
     return run_tests(tests)
 
+
 if __name__ == '__main__':
     sys.exit(main())