I tested vdsm 4.20.0-228.git4739c81 on f25 and noticed that engine nor mom is  not able to connect due to vdsm:

I see

2017-01-17 17:49:53,826 ERROR (Reactor thread) [vds.dispatcher] uncaptured python exception, closing channel <yajsonrpc.betterAsyncore.Dispatcher ('::ffff:192.168.1.105', 39378, 0, 0) at 0x7fdc180d6ab8> (<type 'exceptions.TypeError'>:an integer is required [/usr/lib64/python2.7/asyncore.py|readwrite|108] [/usr/lib64/python2.7/asyncore.py|handle_read_event|449] [/usr/lib/python2.7/site-packages/yajsonrpc/betterAsyncore.py|handle_read|67] [/usr/lib/python2.7/site-packages/yajsonrpc/betterAsyncore.py|_delegate_call|149] [/usr/lib/python2.7/site-packages/vdsm/protocoldetector.py|handle_read|142] [/usr/lib/python2.7/site-packages/yajsonrpc/stompreactor.py|handle_socket|487] [/usr/lib/python2.7/site-packages/vdsm/rpc/bindingjsonrpc.py|add_socket|49] [/usr/lib/python2.7/site-packages/yajsonrpc/stompreactor.py|createListener|454] [/usr/lib/python2.7/site-packages/yajsonrpc/stompreactor.py|StompListener|420] [/usr/lib/python2.7/site-packages/yajsonrpc/betterAsyncore.py|__init__|43] [/usr/lib/python2.7/site-packages/yajsonrpc/betterAsyncore.py|switch_implementation|82] [/usr/lib/python2.7/site-packages/yajsonrpc/stompreactor.py|init|435] [/usr/lib64/python2.7/asyncore.py|set_reuse_addr|313] [/usr/lib64/python2.7/site-packages/M2Crypto/SSL/Connection.py|getsockopt|414] [/usr/lib64/python2.7/socket.py|meth|228]) (betterAsyncore:160)

which changes to infinitive loop:

2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)
2017-01-17 17:50:24,093 WARN  (JsonRpc (StompReactor)) [vds.dispatcher] unhandled read event (betterAsyncore:160)

We need to make sure that vdsm is able to use newer version of m2crypto:

Name        : m2crypto
Arch        : x86_64
Epoch       : 0
Version     : 0.25.1
Release     : 1.fc25