Fix exception leaving app in IO block (use non-blocing IO to teardown writer)

pipe_io_server/pipe_writer_thread.py

@@ -1,5 +1,8 @@
-from threading import Thread
+from contextlib import suppress
+from os import O_NONBLOCK, O_RDONLY, close
+from os import open as osopen
 from queue import Queue
+from threading import Thread
 
 from .terminate_process_on_failure import terminate_process_on_failure
 
@@ -34,4 +37,6 @@ class PipeWriterThread(Thread):
 
     def unblock(self):
         self._write_queue.put(None)
-        open(self._pipe_path, 'rb').close()
+        with suppress(OSError):
+            fd = osopen(self._pipe_path, O_RDONLY | O_NONBLOCK)
+            close(fd)