salt: KeyError: 'saltutil.is_running' on 2015.8.1

I just upgraded my salt-master and one salt-minion to 2015.8.1 to troubleshoot https://github.com/saltstack/salt/issues/27414 with @rallytime, and noticed a new error when trying to run commands like salt phx1-1 state.highstate:

root@phx1-8:/srv/salt# salt phx1-1 state.highstate
phx1-1:
    The minion function caused an exception: Traceback (most recent call last):
      File "/usr/lib/python2.7/dist-packages/salt/minion.py", line 1161, in _thread_return
        data['arg'][ind],
      File "/usr/lib/python2.7/dist-packages/salt/modules/state.py", line 498, in highstate
        conflict = _check_queue(queue, kwargs)
      File "/usr/lib/python2.7/dist-packages/salt/modules/state.py", line 156, in _check_queue
        conflict = running()
      File "/usr/lib/python2.7/dist-packages/salt/modules/state.py", line 119, in running
        active = __salt__['saltutil.is_running']('state.*')
      File "/usr/lib/python2.7/dist-packages/salt/utils/lazy.py", line 90, in __getitem__
        return self._dict[key]
    KeyError: 'saltutil.is_running'
root@phx1-8:/srv/salt#

Based on the minion logs, it does seem to actually execute the requested highstate, but never returns any output to the master that made the request.

If I execute the same commands locally on the minion using salt-call, I don’t see this issue.

Is this a known issue? Am I doing something wrong with my upgrade process? (I followed https://docs.saltstack.com/en/latest/topics/installation/ubuntu.html).

root@phx1-8:/srv/salt# salt --versions-report
Salt Version:
           Salt: 2015.8.1

Dependency Versions:
         Jinja2: 2.7.2
       M2Crypto: 0.21.1
           Mako: 0.9.1
         PyYAML: 3.10
          PyZMQ: 14.4.0
         Python: 2.7.6 (default, Jun 22 2015, 17:58:13)
           RAET: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.0.4
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: 1.5
          gitdb: 0.5.4
      gitpython: 0.3.2 RC1
          ioflo: Not Installed
        libnacl: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.3.0
   mysql-python: 1.2.3
      pycparser: Not Installed
       pycrypto: 2.6.1
         pygit2: Not Installed
   python-gnupg: Not Installed
          smmap: 0.8.2
        timelib: Not Installed

System Versions:
           dist: Ubuntu 14.04 trusty
        machine: x86_64
        release: 3.16.0-48-generic
         system: Ubuntu 14.04 trusty

scott@phx1-1:/var/log/salt$ salt-minion --versions-report
Salt Version:
           Salt: 2015.8.1

Dependency Versions:
         Jinja2: 2.7.2
       M2Crypto: 0.21.1
           Mako: 0.9.1
         PyYAML: 3.10
          PyZMQ: 14.4.0
         Python: 2.7.6 (default, Jun 22 2015, 17:58:13)
           RAET: Not Installed
        Tornado: 4.2.1
            ZMQ: 4.0.4
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: 1.5
          gitdb: 0.5.4
      gitpython: 0.3.2 RC1
          ioflo: Not Installed
        libnacl: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.3.0
   mysql-python: 1.2.3
      pycparser: Not Installed
       pycrypto: 2.6.1
         pygit2: Not Installed
   python-gnupg: Not Installed
          smmap: 0.8.2
        timelib: Not Installed

System Versions:
           dist: Ubuntu 14.04 trusty
        machine: x86_64
        release: 3.16.0-45-generic
         system: Ubuntu 14.04 trusty