Bootstrapping new clients fails with error "unable to parse json"

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Environment

SUSE Manager 5.0

Situation

When bootstrapping new client via webUi it fails.

In /var/log/rhn/rhn_web_ui.log below error message is logged:

ERROR com.suse.manager.webui.controllers.bootstrap.AbstractMinionBootstrapper - Error during bootstrap: An error has occurred during salt execution: unable to parse json.

Within salt api log we see a stack trace with following error message:

jinja2.exceptions.UndefinedError: 'str object' has no attribute 'get'

Enabling trace on salt-api as follows:

mkdir /etc/systemd/system/salt-api.service.d/
cat << EOF > /etc/systemd/system/salt-api.service.d/logging.conf
[Service]
ExecStart=
ExecStart=/usr/bin/salt-api --log-file-level=trace
EOF
systemctl daemon-reload
systemctl restart salt-api.service

If we try again to bootstrap further details are logged:

YYYY-MM-DD hh:mm:ss,ms [salt.utils.vt.Terminal.PID-<PID>.STDOUT:<PID> ][TRACE   ][<PID>] 
MWarning: the ECDSA host key for 'xxxxxxx' differs from the key for t
Offending key for IP in /var/lib/salt/.ssh/known_hosts:225
Matching host key in /var/lib/salt/.ssh/known_hosts:223

Resolution

Removing the host key from:

/var/lib/salt/.ssh/known_hosts

Cause

The client uses an host key which is already known.

Disclaimer

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