Avoiding problems like "'StreamToQueue' object has no attribute 'isatty'" downstream

[pevogam]

As Avocado's runners are replacing the stdout and stderr of the tests with a custom StreamToQueue class, it might be a better idea if this StreamToQueue inherits from or has behavior that is more compatible with python's default stdout. A test script or test utility downstream might for instance do if stdout.isatty that will result in breakage because it might not necessarily assume Avocado has swapped the output channels (e.g. if the code is used in more general scopes beyond avocado). Do you think we should make the StreamToQueue objects more compatible with stdout objects or do you think there is a problem in the argument here?