[logging.RotatingFileHandler] The RotatingFileHandler opens and closes file for each message

**Bug description**
[RotatingFileHandler](https://github.com/pfalcon/pycopy-lib/blob/master/logging/logging/handlers.py#L19) logging handler opens and closes the log file for every message: [line #61](https://github.com/pfalcon/pycopy-lib/blob/master/logging/logging/handlers.py#L61).

**Proposal**
* Open the file once in the constructor.
* Close the file only when rotation happens.