Commit 9db8eecac1 improved the
assert_raises_jsonrpc() function for better testing of RPC failure
modes. This commit completes the job by removing remaining broken
try-except RPC testing from the individual test cases and replacing it
with calls to assert_raises_jsonrpc().
Segwit's version bit will be signalled for all invocations of CreateNewBlock,
and not specifying segwit only will cause CreateNewBlock to skip transactions
with witness from being selected.
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.