[salt-ssh] No module named 'salt.exceptions'

Description of Issue

Hi,

I have three identical nodes (lets say agentless minions).
One of nodes stops to execute calls like this:
salt-ssh 'one-*' grains.get 'kernelrelease'

the following error has appeared:

    _error:
        Failed to return clean data
    retcode:
        1
    stderr:
        Traceback (most recent call last):
          File "/var/tmp/.sadm_2296c1_salt/salt-call", line 26, in <module>
            from salt.scripts import salt_call
          File "/var/tmp/.sadm_2296c1_salt/pyall/salt/scripts.py", line 21, in <module>
            from salt.exceptions import SaltSystemExit, SaltClientError, SaltReqTimeoutError
        ModuleNotFoundError: No module named 'salt.exceptions'

cmd-run call also stops to execute but "salt-ssh -r ..." executes successfully.

The rest two nodes are okay.
Nodes (minions): CentOS Linux release 7.6.1810 (Core)

Could you help to solve this issue?

Versions Report

Master

Salt Version:
           Salt: 2019.2.0
 
Dependency Versions:
           cffi: Not Installed
       cherrypy: Not Installed
       dateutil: Not Installed
      docker-py: Not Installed
          gitdb: Not Installed
      gitpython: Not Installed
          ioflo: Not Installed
         Jinja2: 2.10.1
        libgit2: Not Installed
        libnacl: Not Installed
       M2Crypto: Not Installed
           Mako: Not Installed
   msgpack-pure: Not Installed
 msgpack-python: 0.6.1
   mysql-python: Not Installed
      pycparser: Not Installed
       pycrypto: Not Installed
   pycryptodome: Not Installed
         pygit2: Not Installed
         Python: 3.7.3 (default, Jun 24 2019, 04:54:02)
   python-gnupg: Not Installed
         PyYAML: 5.1.1
          PyZMQ: Not Installed
           RAET: Not Installed
          smmap: Not Installed
        timelib: Not Installed
        Tornado: 4.5.3
            ZMQ: Not Installed
 
System Versions:
           dist: arch Manjaro Linux
         locale: UTF-8
        machine: x86_64
        release: 4.19.62-1-MANJARO
         system: Linux
        version: arch Manjaro Linux

Start by reproducing salt-ssh 'one-*' grains.get 'kernelrelease' and the cmd-run call on the affected and working CentOS nodes. Trace the generated salt-call entry point through salt/scripts.py and its import of salt.exceptions, comparing the transferred files or environment between nodes. Done means these calls complete without ModuleNotFoundError while salt-ssh -r continues to work.