bitbake: asyncrpc: serv: correct closed client socket detection

If the client socket is closed, asyncio.StreamReader.readline() will
return an empty bytes object, not None.

This prevents multiple tracebacks being logged by bitbake-hashserv each
time bitbake is started and performs a connection check.

(Bitbake rev: 2d07f252704dff7747fa1f9adf223a452806717f)

Signed-off-by: Justin Bronder <jsbronder@cold-front.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/asyncrpc/serv.py

@@ -42,7 +42,7 @@ class AsyncServerConnection(object):
 
             # Read protocol and version
             client_protocol = await self.reader.readline()
-            if client_protocol is None:
+            if not client_protocol:
                 return
 
             (client_proto_name, client_proto_version) = client_protocol.decode('utf-8').rstrip().split()
@@ -59,7 +59,7 @@ class AsyncServerConnection(object):
             # an empty line to signal the end of the headers
             while True:
                 line = await self.reader.readline()
-                if line is None:
+                if not line:
                     return
 
                 line = line.decode('utf-8').rstrip()