improve comment

IPython/utils/tests/test_text.py

@@ -21,7 +21,7 b' import nose.tools as nt'
 try:
     from pathlib import Path
 except ImportError:
-    # Python 2 backport
+    # for Python 3.3
     from pathlib2 import Path
 
 from IPython.utils import text

IPython/utils/text.py

@@ -16,7 +16,7 b' from string import Formatter'
 try:
     from pathlib import Path
 except ImportError:
-    # Python 2 backport
+    # for Python 3.3
     from pathlib2 import Path
 
 from IPython.utils import py3compat