TString and pystr concatenation in cmake

While making sure that the cmake tests run in the CI, it has been revealed that there is a problem when concatenating a pystring and a TString.

Excerpt from CI:

14: ======================================================================
14: FAIL: test_pystr_TString (__main__.TStringTest)
14: ----------------------------------------------------------------------
14: Traceback (most recent call last):
14:   File "/atlas-caf/CAFCore/QFramework/test/TString.py", line 18, in test_pystr_TString
14:     self.assertIsInstance(s, str)
14: AssertionError: '1World1Hello ' is not an instance of <type 'str'>
14: 
14: ----------------------------------------------------------------------

The corresponding test code is

s = "1Hello " + TString("1World")
self.assertIsInstance(s, str)
self.assertEqual(s, "1Hello 1World")

Obviously, the string is concatenated in the wrong order. The strange thing about this is, that it works for RC test_pystr_TString (TString.TStringTest) ... ok