- emit DeprecationWarning for mtacceptor [ci skip]

src/ZEO/StorageServer.py

@@ -50,6 +50,8 @@ from ZODB.utils import oid_repr, p64, u64, z64, Lock, RLock
 
 # BBB mtacceptor is unused and will be removed in ZEO version 6
 if os.environ.get("ZEO_MTACCEPTOR"): # mainly for tests
+    warnings.warn('The mtacceptor module is deprecated and will be removed '
+                  'in ZEO version 6.', DeprecationWarning)
     from .asyncio.mtacceptor import Acceptor
 else:
     from .asyncio.server import Acceptor