Substrate runner says PASS when in fact substrate test did not pass

[Marco Ceppi]

Substrate: charm-testing-aws: PASS

Warning: Permanently added '10.0.3.232' (ECDSA) to the list of known hosts.
+ cd /home/ubuntu/charms/mongodb
+ juju destroy-environment -y -e charm-testing-aws
WARNING unknown config field "test-mode"
+ '[' -n False ']'
+ failfast=--set-e
+ charm test -v -e charm-testing-aws --set-e --timeout=45m
juju-test INFO : Starting test run on charm-testing-aws using Juju 1.16.6
juju-test DEBUG : Loading configuration options from testplan YAML
juju-test DEBUG : Creating a new Conductor
juju-test.conductor DEBUG : Starting a bootstrap for charm-testing-aws, kill after 300
juju-test.conductor DEBUG : Running the following: juju bootstrap -e charm-testing-aws
WARNING unknown config field "test-mode"
WARNING unknown config field "test-mode"
WARNING unknown config field "test-mode"
juju-test.conductor DEBUG : Waiting for bootstrap
juju-test.conductor DEBUG : Still not bootstrapped
juju-test.conductor DEBUG : Running the following: juju status -e charm-testing-aws
WARNING unknown config field "test-mode"
WARNING unknown config field "test-mode"
juju-test.conductor DEBUG : State for 1.16.6: down
juju-test.conductor DEBUG : Still not bootstrapped
juju-test.conductor DEBUG : Running the following: juju status -e charm-testing-aws
WARNING unknown config field "test-mode"
WARNING unknown config field "test-mode"
juju-test.conductor DEBUG : State for 1.16.6: started
juju-test.conductor.10-unit.test DEBUG : Running 10-unit.test (tests/10-unit.test)
test_write_log_rotate_config (unittest.loader.ModuleImportFailure) ... ERROR

======================================================================
ERROR: test_write_log_rotate_config (unittest.loader.ModuleImportFailure)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_write_log_rotate_config
Traceback (most recent call last):
  File "/usr/lib/python2.7/unittest/loader.py", line 252, in _find_tests
    module = self._get_module_from_name(name)
  File "/usr/lib/python2.7/unittest/loader.py", line 230, in _get_module_from_name
    __import__(name)
  File "/home/ubuntu/charms/mongodb/tests/test_write_log_rotate_config.py", line 2, in <module>
    import mock
ImportError: No module named mock

----------------------------------------------------------------------
Ran 1 test in 0.005s

FAILED (errors=1)
juju-test.conductor.10-unit.test DEBUG :
juju-test.conductor.10-unit.test DEBUG : Got exit code: 1
juju-test.conductor.10-unit.test RESULT : ���
juju-test.conductor INFO : Breaking here as requested by --set-e
juju-test INFO : Results: 0 passed, 1 failed, 0 errored

Substrate: charm-testing-aws: should report a fail not a pass for the aws test