Fixed stats issue with tcpkiss client.

The tcpkiss client's stats method wasn't serializing all of
the datetime objects.  This patch ensures that all the dates
in the stats are serializable when requested.

aprsd/client/drivers/aprsis.py

@@ -180,7 +180,7 @@ class APRSISDriver:
             LOG.warning('client is None, might be resetting.')
             self.connected = False
 
-    def stats(self, serializable=False) -> dict:
+    def stats(self, serializable: bool = False) -> dict:
         stats = {}
         if self.is_configured():
             if self._client:

aprsd/client/drivers/tcpkiss.py

@@ -271,8 +271,19 @@ class TCPKISSDriver:
         """
         if serializable:
             keepalive = self.keepalive.isoformat()
+            if self.last_packet_sent:
+                last_packet_sent = self.last_packet_sent.isoformat()
+            else:
+                last_packet_sent = 'None'
+            if self.last_packet_received:
+                last_packet_received = self.last_packet_received.isoformat()
+            else:
+                last_packet_received = 'None'
         else:
             keepalive = self.keepalive
+            last_packet_sent = self.last_packet_sent
+            last_packet_received = self.last_packet_received
+
         stats = {
             'client': self.__class__.__name__,
             'transport': self.transport,
@@ -280,8 +291,8 @@ class TCPKISSDriver:
             'path': self.path,
             'packets_sent': self.packets_sent,
             'packets_received': self.packets_received,
-            'last_packet_sent': self.last_packet_sent,
-            'last_packet_received': self.last_packet_received,
+            'last_packet_sent': last_packet_sent,
+            'last_packet_received': last_packet_received,
             'connection_keepalive': keepalive,
             'host': CONF.kiss_tcp.host,
             'port': CONF.kiss_tcp.port,