Make build less flaky

[rinslow]

A successful build will fail every now and then for multiprocess reasons.
Here's a helpful traceback:

================================== FAILURES ===================================
____ TestMultiprocessTimeouts.test_suite_continues_after_teardown_timeout _____
self = <tests.core.multiprocess.test_timeout.TestMultiprocessTimeouts testMethod=test_suite_continues_after_teardown_timeout>
    def test_suite_continues_after_teardown_timeout(self):
        """Test that tests continue to run after a case is killed in tearDown.
    
            * Create a suite composed of a case which gets timeout during tearDown
                and a case which run successfully.
            * Validate that the first case was killed in time.
            * Validate that the second case was run.
            """
        TearDownTimeoutCase.pid_queue = self.pid_queue
        TearDownTimeoutCase.post_timeout_event = self.post_timeout_event
    
        BasicMultiprocessCase.pid_queue = self.pid_queue
        BasicMultiprocessCase.post_timeout_event = self.post_timeout_event
    
        MockSuite1.components = (TearDownTimeoutCase,)
        MockSuite2.components = (BasicMultiprocessCase,)
    
        MockTestSuite.components = (MockSuite1, MockSuite2)
    
        self.runner.run(MockTestSuite)
    
        self.assertFalse(self.post_timeout_event.is_set(),
                         "Process continued when it should have been "
                         "terminated due to timeout")
    
>       self.validate_test_processes(2)
tests\core\multiprocess\test_timeout.py:133: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
tests\core\multiprocess\test_runner.py:70: in validate_test_processes
    "Process %s wasn't killed" % pid)
E   AssertionError: Process 2052 wasn't killed
_________ TestMultiprocessTimeouts.test_suite_continues_after_timeout _________
self = <tests.core.multiprocess.test_timeout.TestMultiprocessTimeouts testMethod=test_suite_continues_after_timeout>
    def test_suite_continues_after_timeout(self):
        """Test that a test suite continues to run after a case is killed.
    
            * Create a suite composed of a case which gets timeout and a case which
                  run successfully.
            * Validate that the first case was killed in time.
            * Validate that the second case was run.
            """
        TimeoutCase.pid_queue = self.pid_queue
        TimeoutCase.post_timeout_event = self.post_timeout_event
    
        BasicMultiprocessCase.pid_queue = self.pid_queue
        BasicMultiprocessCase.post_timeout_event = self.post_timeout_event
    
        MockSuite1.components = (TimeoutCase,)
        MockSuite2.components = (BasicMultiprocessCase,)
    
        MockTestSuite.components = (MockSuite1, MockSuite2)
    
        self.runner.run(MockTestSuite)
    
        self.assertFalse(self.post_timeout_event.is_set(),
                         "Process continued when it should have been "
                         "terminated due to timeout")
    
>       self.validate_test_processes(2)
tests\core\multiprocess\test_timeout.py:106: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
tests\core\multiprocess\test_runner.py:70: in validate_test_processes
    "Process %s wasn't killed" % pid)
E   AssertionError: Process 652 wasn't killed
======== 2 failed, 202 passed, 3 skipped, 4 warnings in 279.36 seconds ========
ERROR: InvocationError: 'C:\\projects\\rotest\\.tox\\py27-win32\\Scripts\\pytest.EXE tests

[gregoil]

https://ci.appveyor.com/project/gregoil/rotest/builds/19909212/job/sj9b9pj4kt4kgdax