stop zmq garbage collection to avoid threadsafety issues

when cleaning up all zmq resources

Author: minrk

jupyter_client/tests/conftest.py

@@ -50,6 +50,11 @@ def assert_no_zmq():
     avoids reference leaks across tests,
     which can lead to FD exhaustion
     """
+    # zmq garbage collection uses a zmq socket in a thread
+    # we don't want to delete these from the main thread!
+    from zmq.utils import garbage
+
+    garbage.gc.stop()
     sockets = [
         obj
         for obj in gc.get_referrers(zmq.Socket)