sys.state_schema returning error for example command

Issue

I am trying out salt \* sys.state_schema pkg.installed, which is the example command to try out sys.state_schema and am receiving an error.

root@[omitted]# salt \* sys.state_schema pkg.installed
local-minion:
    Passed invalid arguments to sys.state_schema: type() argument 1 must be string, not unicode
    
        Return a JSON Schema for the given state function(s)
    
        .. versionadded:: 2016.3.0
    
        CLI Example:
    
        .. code-block:: bash
    
            salt '*' sys.state_schema
            salt '*' sys.state_schema pkg.installed

also tried these variations (which also returned with same error):

salt '*' sys.state_schema pkg.installed
salt 'local-minion' sys.state_schema pkg.installed
salt '*' sys.state_schema 'pkg.installed'
salt 'local-minion' sys.state_schema 'pkg.installed'

Salt info

root@[omitted]# salt --versions-report
Salt Version:
           Salt: 2019.2.0
 
Dependency Versions:
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: 2.6.1
      docker-py: Not Installed
          gitdb: 2.0.3
      gitpython: 2.1.8
          ioflo: Not Installed
         Jinja2: 2.10
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: Not Installed
           Mako: 1.0.7
   msgpack-pure: Not Installed
 msgpack-python: 0.5.6
   mysql-python: Not Installed
      pycparser: Not Installed
       pycrypto: 2.6.1
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 2.7.15+ (default, Nov 27 2018, 23:36:35)
   python-gnupg: 0.4.1
         PyYAML: 3.12
          PyZMQ: 16.0.2
           RAET: Not Installed
          smmap: 2.0.3
        timelib: Not Installed
        Tornado: 4.5.3
            ZMQ: 4.2.5
 
System Versions:
           dist: Ubuntu 18.04 bionic
         locale: UTF-8
        machine: x86_64
        release: 4.15.0-54-generic
         system: Linux
        version: Ubuntu 18.04 bionic

Start by reproducing the documented salt '*' sys.state_schema pkg.installed command and compare it with the reported type() argument 1 must be string, not unicode error. Trace the sys.state_schema entry point referenced in the Salt documentation and verify that the example command completes successfully without the argument error.