Add test-case that motivates the broken scenario for the existing fla…

…tten

It fails when it's nested several levels.  Also fix a unit test broken
by the current change that relied on only list being flattened by
default

master/buildbot/test/unit/test_util.py

@@ -236,9 +236,19 @@ def test_deep(self):
         self.assertEqual(util.flatten([[1, 2], 3, [[4]]]),
                          [1, 2, 3, 4])
 
+    def test_deeply_nested(self):
+        self.assertEqual(util.flatten([5, [6, (7, 8)]]),
+                         [5, 6, 7, 8])
+
     def test_tuples(self):
-        self.assertEqual(util.flatten([(1, 2), 3]), [(1, 2), 3])
+        self.assertEqual(util.flatten([(1, 2), 3]), [1, 2, 3])
+
+    def test_dict(self):
+        d = {'a': [5, 6, 7], 'b': [7, 8, 9]}
+        self.assertEqual(util.flatten(d), d)
 
+    def test_string(self):
+        self.assertEqual(util.flatten("abc"), "abc")
 
 class Ascii2Unicode(unittest.TestCase):