CLN: Change assert_([not] isinstance(a,b)) to specialized forms

Work on pandas-dev#6175. Change superclass of tests/test_compat, to use tm.TestCase

Author: bwignall

pandas/tests/test_compat.py

@@ -11,7 +11,7 @@
 import nose
 import pandas.util.testing as tm
 
-class TestBuiltinIterators(unittest.TestCase):
+class TestBuiltinIterators(tm.TestCase):
     def check_result(self, actual, expected, lengths):
         for (iter_res, list_res), exp, length in zip(actual, expected, lengths):
             self.assertNotIsInstance(iter_res, list)