Coerce the small bytes header of a message to bytes

mrocklin · mrocklin · commit 44c1d5cc6a86 · 2019-04-17T11:49:33.000-07:00
UCX was producing memoryviews here, and they seemed to be malformed.
Coercing to bytes seems foolproof and cheap (these should always be small)
diff --git a/distributed/protocol/core.py b/distributed/protocol/core.py
@@ -192,6 +192,7 @@ def loads_msgpack(header, payload):
     See Also:
         dumps_msgpack
     """
+    header = bytes(header)
     if header:
         header = msgpack.loads(header, use_list=False, **msgpack_opts)
     else:
