Replace deprecated assertRaisesRegexp

The assertRaisesRegexp method has been deprecated since it was renamed
to assertRaisesRegex in Python 3.2.

https://docs.python.org/3/library/unittest.html#deprecated-aliases

Change-Id: Ibab4d14764372298cc0055f168ff44eabdc873f0

Author: wu.shiming

cloudkittyclient/tests/functional/v2/test_dataframes.py

@@ -137,7 +137,7 @@ def tearDown(self):
         super(CkDataframesTest, self).tearDown()
 
     def test_dataframes_add_with_no_args(self):
-        self.assertRaisesRegexp(
+        self.assertRaisesRegex(
             RuntimeError,
             'error: the following arguments are required: datafile',
             self.runner,