[test][stats] Code cleanup

beat/core/test/test_stats.py

@@ -41,8 +41,8 @@ from ..stats import Statistics
 def test_prototype():
     obj = Statistics()  # creates from prototype
 
-    assert "cpu" in obj._data
-    assert "memory" in obj._data
-    assert "data" in obj._data
-    assert "files" in obj.data
+    nose.tools.assert_true("cpu" in obj._data)
+    nose.tools.assert_true("memory" in obj._data)
+    nose.tools.assert_true("data" in obj._data)
+    nose.tools.assert_true("files" in obj.data)
     nose.tools.eq_(len(obj.data["files"]), 0)