derive Exit from KeyboardInterrupt to simplify exception catching

--HG--
branch : trunk

py/test/testing/test_outcome.py

@@ -76,6 +76,13 @@ def test_importorskip():
         print py.code.ExceptionInfo()
         py.test.fail("spurious skip")
 
+def test_pytest_exit():
+    try:
+        py.test.exit("hello")
+    except:
+        excinfo = py.code.ExceptionInfo()
+        assert excinfo.errisinstance(KeyboardInterrupt)
+
 def test_pytest_mark_getattr():
     from py.__.test.outcome import mark
     def f(): pass