This commit fixes the module-level docstrings for the tests and helper
modules in qa. Many of these tests were uncommented previously - this
commit ensures that every test case has at least a minimum level of
commenting.
Make sure that RPC tests are actually checking failures correctly by:
- Catching JSON RPC exceptions and verifying the error codes and messages.
- Failing the test case if the JSON RPC exception isn't raised.
John Newbery