set user agent

Signed-off-by: Thiago Rondon <thiago.rondon@gmail.com>
_validate_key

Signed-off-by: Thiago Rondon <thiago.rondon@gmail.com>
_validate_path

Signed-off-by: Thiago Rondon <thiago.rondon@gmail.com>
_log_info, _log_warn and _log_error

Signed-off-by: Thiago Rondon <thiago.rondon@gmail.com>