Fix pickling issue in file_writer on macOS

asciinema/file_writer.py

@@ -11,7 +11,7 @@ class file_writer:
     ) -> None:
         self.path = path
         self.file: Optional[IO[Any]] = None
-        self.on_error = on_error or (lambda _x: None)
+        self.on_error = on_error or noop
 
     def __enter__(self) -> Any:
         self._open_file()
@@ -38,3 +38,7 @@ class file_writer:
             else:
                 self.on_error("Output pipe broken")
                 raise e
+
+
+def noop(_: Any) -> None:
+    return None

asciinema/recorder.py

@@ -55,7 +55,7 @@ def record(  # pylint: disable=too-many-arguments,too-many-locals
         )
 
         sync_writer = writer(
-            path_, metadata, append, on_error=_notifier.notify
+            path_, metadata, append, on_error=_notifier.queue.put
         )
 
         with async_writer(sync_writer, time_offset, record_stdin) as _writer: