Add support for Robot's programmatic logging APIs

[mulmschneider]

As far as I can tell, the way how logging works in combination with the PythonRemoteServer depends very much on when the corresponding logging StreamHandler is first created.
If it is created before _intercept_std_streams() is called, then the logging output will be sent to stderr of the server. If it is created after _intercept_std_streams(), then the output is sent as output to the calling client.

I fixed this for my use case with this change to _intercept_std_streams(), which makes sure that I receive all log messages logged during run_keyword() on the robotframework client:

    def _intercept_std_streams(self):
        sys.stdout = StringIO()
        sys.stderr = StringIO()
        # reset the logging handler so that it is connected to the right stderr stream
        import logging
        logging.getLogger().handlers = []
        ch = logging.StreamHandler()
        logging.getLogger().addHandler(ch)

NOTE: I mostly opened this issue so that it is documented in case other people run into similiar problems. I'm not sure if this is something that can/should be handled by the default implementation of PythonRemoteServer, since you would have to consider a myriad of possible python logging configurations. Feel free to close.

[pekkaklarck]

Yeah, the remote server only supports logging via stdout/stderr. Some kind of support for Robot's own robot.api.logger API and Python's standard logging module would be nice.

[pekkaklarck]

Oh, #26 proposes the exact same thing. Closing this as a duplicate.