address reviewer comments

doc/en/usage.txt

@@ -88,8 +88,16 @@ failure situation::
     py.test --pdb --maxfail=3  # drop to PDB for first three failures
 
 Note that on any failure the exception information is stored on 
-``sys.last_traceback``. In interactive use, this allows one to drop
-into postmortem debugging with any debug tool.
+``sys.last_value``, ``sys.last_type`` and ``sys.last_traceback``. In
+interactive use, this allows one to drop into postmortem debugging with
+any debug tool. One can also manually access the exception information,
+for example::
+
+    >> import sys
+    >> sys.last_traceback.tb_lineno
+    42
+    >> sys.last_value
+    AssertionError('assert result == "ok"',)
 
 Setting a breakpoint / aka ``set_trace()``
 ----------------------------------------------------

testing/test_runner.py

@@ -527,7 +527,10 @@ def test_makereport_getsource(testdir):
     result.stdout.fnmatch_lines(['*else: assert False*'])
 
 
-def test_store_except_info_on_eror(testdir):
+def test_store_except_info_on_eror():
+    """ Test that upon test failure, the exception info is stored on
+    sys.last_traceback and friends.
+    """
     # Simulate item that raises a specific exception
     class ItemThatRaises:
         def runtest(self):