Give fake OK response to OPTIONS pinentry-mode=ask

pinentry-mode=ask is the default, so this is a no-op.  Return OK instead
of an error code.  Sequoia Chameleon sends pinentry-mode=ask and
disconnects when it gets an error.

Fixes: QubesOS/qubes-issues#9528

Author: DemiMarie

splitgpg2/__init__.py

@@ -679,6 +679,11 @@ async def command_OPTION(self, untrusted_args: Optional[bytes]) -> None:
         if not untrusted_args:
             raise Filtered
 
+        if untrusted_args == b'pinentry-mode=ask':
+            # This is the default and a no-op
+            self.fake_respond(b'OK')
+            return
+
         untrusted_name, untrusted_value = extract_args(untrusted_args, b'=')
         try:
             action, opts = self.options[untrusted_name]