Add support for sending unsolicited messages from device

This is used in the gamry device. It sends a "charge complete"
message some seconds after being sent a command to "start charging".

This is accomplished by code similar to the following
in the device StreamInterface:

    def charged(self):
        self.handler.unsolicitedReply("STOPPED")

    def start_charging(self):
        t = Timer(self.charging_time, self.charged)
        t.start()
        return "STARTED"

Author: FreddieAkeroyd

src/lewis/adapters/stream.py

@@ -43,6 +43,7 @@ def __init__(self, sock, target, stream_server):
         self._buffer = []
 
         self._stream_server = stream_server
+        self._target.handler = self
 
         self._set_logging_context(target)
         self.log.info('Client connected from %s:%s', *sock.getpeername())
@@ -108,6 +109,10 @@ def found_terminator(self):
 
         self._send_reply(reply)
 
+    def unsolicitedReply(self, reply):
+        self.log.debug('Sending unsolicited reply %s', reply)
+        self.push(b(reply + self._target.out_terminator))
+
     def handle_close(self):
         self.log.info('Closing connection to client %s:%s', *self.socket.getpeername())
         self._stream_server.remove_handler(self)