Rework PipeIOServer to use "keep pipes open" model with robust unblocking

pipe_io_server/pipe_writer_thread.py

@@ -2,13 +2,13 @@ from threading import Thread
 from queue import Queue
 
 from .terminate_process_on_failure import terminate_process_on_failure
-from .pipe import Pipe
 
 
 class PipeWriterThread(Thread):
-    def __init__(self, pipe_path):
+    def __init__(self, pipe_path, stop_event):
         super().__init__()
         self._pipe_path = pipe_path
+        self._stop_event = stop_event
         self._write_queue = Queue()
 
     def write(self, message):
@@ -16,12 +16,22 @@ class PipeWriterThread(Thread):
 
     @terminate_process_on_failure
     def run(self):
-        while True:
-            message = self._write_queue.get(block=True)
-            if message is None:
-                break
-            Pipe(self._pipe_path).write(message)
+        try:
+            with open(self._pipe_path, 'w') as pipe:
+                while True:
+                    message = self._write_queue.get(block=True)
+                    if message is None:
+                        self._stop_event.set()
+                        break
+                    pipe.write(f'{message}\n')
+                    pipe.flush()
+        except BrokenPipeError:
+            self._stop_event.set()
 
     def stop(self):
-        self._write_queue.put(None)
+        self.unblock()
         self.join()
+
+    def unblock(self):
+        self._write_queue.put(None)
+        open(self._pipe_path, 'r').close()