python/qemu/qmp.py: re-raise OSError when encountered

Nested if conditions don't change when the exception block fires; we
need to explicitly re-raise the error if we didn't intend to capture and
suppress it.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20201009175123.249009-3-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

python/qemu/qmp.py

@@ -169,10 +169,11 @@ class QEMUMonitorProtocol:
         try:
             self.__json_read()
         except OSError as err:
-            if err.errno == errno.EAGAIN:
-                # No data available
-                pass
-        self.__sock.setblocking(True)
+            # EAGAIN: No data available; not critical
+            if err.errno != errno.EAGAIN:
+                raise
+        finally:
+            self.__sock.setblocking(True)
 
         # Wait for new events, if needed.
         # if wait is 0.0, this means "no wait" and is also implicitly false.