diff --git a/IPython/core/page.py b/IPython/core/page.py
index 31f351a..4a6af2f 100644
--- a/IPython/core/page.py
+++ b/IPython/core/page.py
@@ -69,6 +69,11 @@ def page_dumb(strng, start=0, screen_lines=25):
         print >>io.stdout, last_escape + os.linesep.join(screens[-1])
 
 def _detect_screen_size(use_curses, screen_lines_def):
+    """Attempt to work out the number of lines on the screen.
+    
+    This is called by page(). It can raise an error (e.g. when run in the
+    test suite), so it's separated out so it can easily be called in a try block.
+    """
     if (TERM=='xterm' or TERM=='xterm-color') and sys.platform != 'sunos5':
         local_use_curses = use_curses
     else:
diff --git a/IPython/testing/tools.py b/IPython/testing/tools.py
index 36986ff..053ffba 100644
--- a/IPython/testing/tools.py
+++ b/IPython/testing/tools.py
@@ -325,6 +325,7 @@ def check_pairs(func, pairs):
         out = func(inp)
         assert out == expected, pair_fail_msg.format(name, inp, expected, out)
 
+
 if py3compat.PY3:
     MyStringIO = StringIO
 else:
@@ -337,6 +338,7 @@ else:
 
 notprinted_msg = """Did not find {0!r} in printed output (on {1}):
 {2!r}"""
+
 class AssertPrints(object):
     """Context manager for testing that code prints certain text.