Fix output encoding problems in the test runner with Py2.7 by replacing...

Fix output encoding problems in the test runner with Py2.7 by replacing implicit calls to str() with (unicode) string concatenation.

runtests.py

@@ -1293,9 +1293,9 @@ class CythonCompileTestCase(unittest.TestCase):
                     error = str(exc)
             stderr = prepare_captured(get_stderr())
             if stderr:
-                print(u"Compiler output for module %s:\n%s" % (module, stderr))
+                print(u"Compiler output for module " + module + ":" + stderr)
             if error is not None:
-                raise CompileError(u"%s\nCompiler output:\n%s" % (error, stderr))
+                raise CompileError(error + u"\nCompiler output:\n" + stderr)
         finally:
             os.chdir(cwd)