prevent intermittent broken_pipe errors with threaded=True

Author: mattwbarry

pytest_flask/fixtures.py

@@ -57,7 +57,7 @@ def __init__(self, app, port):
     def start(self):
         """Start application in a separate process."""
         def worker(app, port):
-            app.run(port=port, use_reloader=False)
+            app.run(port=port, use_reloader=False, threaded=True)
         self._process = multiprocessing.Process(
             target=worker,
             args=(self.app, self.port)