Understand Assuan comments

Assuan comments start with '#' and must be ignored.  Do not send them to
the client.

splitgpg2/__init__.py

@@ -1057,6 +1057,9 @@ async def handle_agent_response(self,
         untrusted_line = await self.agent_reader.readline()
         untrusted_line = untrusted_line.rstrip(b'\n')
         self.log_io('A >>>', untrusted_line)
+        if untrusted_line.startswith(b'#'):
+            # Comment, ignore
+            return True
         untrusted_res, untrusted_args = extract_args(untrusted_line)
         if untrusted_res in (b'D', b'S'):
             # passthrough to the client