Fix assert_equal ref

IPython/nbconvert/tests/base.py

@@ -17,6 +17,7 b' import os'
 import glob
 import shutil
 
+from nose.tools import assert_equal
 import IPython
 from IPython.utils.tempdir import TemporaryWorkingDirectory
 from IPython.utils.process import get_output_error_code
@@ -73,7 +74,7 b' class TestsBase(object):'
             a = a.lower()
             b = b.lower()
             
-        self.assertEqual(a, b)
+        assert_equal(a, b)
 
 
     def recursive_replace(self, text, search, replacement):