Add more consitent exception generation and handling

tools/isolate/trace_inputs_test.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import cStringIO
 import logging
 import os
 import unittest
 import sys
@@ skipping 152 matching lines @@
       ]
       command = [
         '/home/foo_bar_user/out/unittests', '--gtest_filter=AtExitTest.Basic',
       ]
       self._test_lines(lines, '/home/foo_bar_user/src', files, command)
 
     def test_empty(self):
       try:
         self._load_context([], None)
         self.fail()
-      except AssertionError:
-        pass
+      except trace_inputs.TracingFailure, e:
+        expected = (
+          'Found internal inconsitency in process lifetime detection',
+          None,
+          None,
+          None,
+          [])
+        self.assertEquals(expected, e.args)
 
     def test_close(self):
       lines = [
         (self._ROOT_PID, 'close(7)                          = 0'),
       ]
       self._test_lines(lines, '/home/foo_bar_user/src', [])
 
     def test_clone(self):
       # Grand-child with relative directory.
       lines = [
@@ skipping 177 matching lines @@
           'size': -1,
         },
       ]
       self._test_lines(lines, '/home/foo_bar_user/src', files)
 
 
 if __name__ == '__main__':
   VERBOSE = '-v' in sys.argv
   logging.basicConfig(level=logging.DEBUG if VERBOSE else logging.ERROR)
   unittest.main()