Remove print statements from Python tests

Use exceptions instead of printing to stdout.
Part of an effort to convert Python tests to python 3 syntax.

Examples/test-suite/python/director_string_runme.py

@@ -18,12 +18,10 @@ b = B("hello")
 
 b.get(0)
 if b.get_first() != "hello world!":
-    print b.get_first()
-    raise RuntimeError
+    raise RuntimeError("b.get_first(): {}".format(b.get_first()))
 
 
 b.call_process_func()
 
 if b.smem != "hello":
-    print smem
-    raise RuntimeError
+    raise RuntimeError("smem: {}".format(smem))