Code review comment for lp:~nobuto/charm-helpers/execd

Reflected review comments, but I found the test is failing with Python 3. I don't know how to handle this, but will look into it.

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FAIL: tests.payload.test_execd.ExecDTestCase.test_execd_run_logs_exception
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testtools.testresult.real._StringException: Traceback (most recent call last):
  File "/home/nobuto/dev/charm-helpers_execd/.venv3/lib/python3.5/site-packages/mock.py", line 1201, in patched
    return func(*args, **keywargs)
  File "/home/nobuto/dev/charm-helpers_execd/tests/payload/test_execd.py", line 142, in test_execd_run_logs_exception
    log_.assert_called_with(expected_log)
  File "/home/nobuto/dev/charm-helpers_execd/.venv3/lib/python3.5/site-packages/mock.py", line 835, in assert_called_with
    raise AssertionError(msg)
AssertionError: Expected call: log('Error (1) running /tmp/tmp11nk64mu/exec.d/basenode/charm-pre-install. Output: stdout_from_pre_install\nstderr_from_pre_install\n')
Actual call: log("Error (1) running /tmp/tmp11nk64mu/exec.d/basenode/charm-pre-install. Output: b'stdout_from_pre_install\\nstderr_from_pre_install\\n'")