venv-salt-minion fails with "salt.ext.tornado.concurrent.Future object at <address>" on startup

SUSE Manager 4.3.15
SUSE Multi Linux Manager 5.0.4
venv-salt-minion-3006.0-1.59.1.x86_64 (SUSE Liberty Linux 9)
venv-salt-minion-3006.0-150000.3.78.1.x86_64 (SLES 15 SP7)

After updating the venv-salt-minion on a minion system connected to a SUSE Manager 4.3.15 or SUSE Multi Linux Manager 5.0.4.1 based system to the latest available version, the minion is no longer able to connect but shows a python trace as follows (either on the console or in /var/log/venv-salt-minion.log):

2025-07-25 08:55:55,309 [tornado.application:300 ][ERROR   ][9027] Exception in callback functools.partial(<function wrap.<locals>.null_wrapper at 0x7f2e993253a0>, <salt.ext.tornado.concurrent.Future object at 0x7f2e9a8a81d0>)
Traceback (most recent call last):
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/ioloop.py", line 606, in _run_callback
    ret = callback()
          ^^^^^^^^^^
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/stack_context.py", line 278, in null_wrapper
    return fn(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/ioloop.py", line 628, in _discard_future_result
    future.result()
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/concurrent.py", line 249, in result
    raise_exc_info(self._exc_info)
  File "<string>", line 4, in raise_exc_info
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/gen.py", line 1064, in run
    yielded = self.gen.throw(*exc_info)
              ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/crypt.py", line 657, in _authenticate
    creds = yield self.sign_in(channel=channel)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/gen.py", line 1056, in run
    value = future.result()
            ^^^^^^^^^^^^^^^
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/concurrent.py", line 249, in result
    raise_exc_info(self._exc_info)
  File "<string>", line 4, in raise_exc_info
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/ext/tornado/gen.py", line 1070, in run
    yielded = self.gen.send(value)
              ^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/crypt.py", line 788, in sign_in
    ret = self.handle_signin_response(sign_in_payload, payload)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/venv-salt-minion/lib64/python3.11/site-packages/salt/crypt.py", line 824, in handle_signin_response
    payload["session"], RSA.pkcs1_oaep_padding
    ~~~~~~~^^^^^^^^^^^
KeyError: 'session'

Please update SUSE Manager to 4.3.16 or SUSE Multi Linux Manager to 5.0.5 first before applying minion updates. 

In this particular case, SUSE Manager 4.3.16 and SUSE Multi Linux Manager 5.0.5 introduce a series of CVE fixes that require the salt master to be patched before applying the minion. 

SUSE Manager 4.3.16 release notes:
https://www.suse.com/releasenotes/x86_64/SUSE-MANAGER/4.3/index.html#_important_salt_security_update

SUSE Manager 4.3.16 refers to the web.version found in

# /bin/grep web.version /usr/share/rhn/config-defaults/rhn_web.conf

web.version = 4.3.16

Update SUSE Manager 4.3 server using

#zypper up

SUSE Multi Linux Manager 5.0.5 release notes:
https://www.suse.com/releasenotes/x86_64/SUSE-MANAGER/5.0/index.html#_important_salt_security_update