zapwallettxes.py test failure due to bitcoind return code

[laanwj]

In #10677 there was what looks like a new kind of Travis false positive, or at least an intermittent error.
It is triggered by the assertion on return code added in #10636:

zapwallettxes.py failed, Duration: 11 s
stdout:
2017-06-27 03:50:43.814000 TestFramework (INFO): Initializing test directory /tmp/bitcoin_test_runner_20170627_034653/zapwallettxes_338
2017-06-27 03:50:46.305000 TestFramework (INFO): Mining blocks...
2017-06-27 03:50:54.465000 TestFramework (ERROR): Assertion failed
Traceback (most recent call last):
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/test_framework.py", line 153, in main
    self.run_test()
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/zapwallettxes.py", line 67, in run_test
    self.stop_node(0)
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/test_framework.py", line 217, in stop_node
    _stop_node(self.nodes[num_node], num_node)
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/util.py", line 326, in _stop_node
    assert_equal(return_code, 0)
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/util.py", line 440, in assert_equal
    raise AssertionError("not(%s)" % " == ".join(str(arg) for arg in (thing1, thing2) + args))
AssertionError: not(1 == 0)
2017-06-27 03:50:54.466000 TestFramework (INFO): Stopping nodes
stderr:
Traceback (most recent call last):
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/authproxy.py", line 126, in _request
    return self._get_response()
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/authproxy.py", line 169, in _get_response
    http_response = self.__conn.getresponse()
  File "/usr/lib/python3.4/http/client.py", line 1208, in getresponse
    response.begin()
  File "/usr/lib/python3.4/http/client.py", line 380, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python3.4/http/client.py", line 350, in _read_status
    raise BadStatusLine(line)
http.client.BadStatusLine: ''
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/zapwallettxes.py", line 80, in <module>
    ZapWalletTXesTest ().main ()
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/test_framework.py", line 172, in main
    self.stop_nodes()
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/test_framework.py", line 220, in stop_nodes
    _stop_nodes(self.nodes)
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/util.py", line 334, in _stop_nodes
    _stop_node(node, i)
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/util.py", line 321, in _stop_node
    node.stop()
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/coverage.py", line 46, in __call__
    return_val = self.auth_service_proxy_instance.__call__(*args, **kwargs)
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/authproxy.py", line 152, in __call__
    response = self._request('POST', self.__url.path, postdata.encode('utf-8'))
  File "/home/travis/build/bitcoin/bitcoin/build/bitcoin-x86_64-unknown-linux-gnu/test/functional/test_framework/authproxy.py", line 130, in _request
    self.__conn.request(method, path, postdata, headers)
  File "/usr/lib/python3.4/http/client.py", line 1125, in request
    self._send_request(method, url, body, headers)
  File "/usr/lib/python3.4/http/client.py", line 1163, in _send_request
    self.endheaders(body)
  File "/usr/lib/python3.4/http/client.py", line 1121, in endheaders
    self._send_output(message_body)
  File "/usr/lib/python3.4/http/client.py", line 951, in _send_output
    self.send(msg)
  File "/usr/lib/python3.4/http/client.py", line 886, in send
    self.connect()
  File "/usr/lib/python3.4/http/client.py", line 863, in connect
    self.timeout, self.source_address)
  File "/usr/lib/python3.4/socket.py", line 512, in create_connection
    raise err
  File "/usr/lib/python3.4/socket.py", line 503, in create_connection
    sock.connect(sa)
ConnectionRefusedError: [Errno 111] Connection refused

I'm not able to reproduce this locally.
It's likely that the node crashed in some way, but this doesn't give enough information to extract what happened.

[laanwj]

Looks like this was a one-time problem, haven't seen it again.

[maflcko]

This is still an issue and I hypothesize it has something to do with setting the return code after a shutdown was requested quickly after startup. Though, I haven't yet looked at a fix...

[jnewbery]

Perhaps we should just comment out zapwallettxes.py for now? zapwallettxes doesn't actually test anything due to a syntax error (will be fixed in #10330)

[maflcko]

Fixed by @TheBlueMatt in #11831