Although not really surprising, it's not just bootstrap that can fail. Here is a case where kill-controller failed:
INFO lib.juju.environment . . All hosted models reclaimed, cleaning up controller machines
INFO lib.juju.environment . . WARNING discovered API versions: [{Version:{major:2 minor:0} Links:[{Href:http://10.96.21.108:8774/v2/ Rel:self}] Status:SUPPORTED} {Versio
n:{major:2 minor:1} Links:[{Href:http://10.96.21.108:8774/v2.1/ Rel:self}] Status:CURRENT}]
INFO lib.juju.environment . . WARNING discovered API versions: [{Version:{major:2 minor:0} Links:[{Href:http://10.96.21.116:9696/v2.0 Rel:self}] Status:CURRENT}]
INFO lib.juju.environment . . ERROR destroying controller model: destroying storage: listing volumes: Get http://10.96.21.114:8776/v2/0e0b4ae2e6724f4ea42ebd018991d360/volumes/detail: EOF
INFO lib.juju.environment . ERROR
...
RuntimeError: Command ('juju', 'kill-controller', '-y', 'osa-controller') exited with status 1 ()
Although not really surprising, it's not just bootstrap that can fail. Here is a case where kill-controller failed: environment . . All hosted models reclaimed, cleaning up controller machines environment . . WARNING discovered API versions: [{Version:{major:2 minor:0} Links:[{Href:http:// 10.96.21. 108:8774/ v2/ Rel:self}] Status:SUPPORTED} {Versio 10.96.21. 108:8774/ v2.1/ Rel:self}] Status:CURRENT}] environment . . WARNING discovered API versions: [{Version:{major:2 minor:0} Links:[{Href:http:// 10.96.21. 116:9696/ v2.0 Rel:self}] Status:CURRENT}] environment . . ERROR destroying controller model: destroying storage: listing volumes: Get http:// 10.96.21. 114:8776/ v2/0e0b4ae2e672 4f4ea42ebd01899 1d360/volumes/ detail: EOF environment . ERROR
INFO lib.juju.
INFO lib.juju.
n:{major:2 minor:1} Links:[{Href:http://
INFO lib.juju.
INFO lib.juju.
INFO lib.juju.
...
RuntimeError: Command ('juju', 'kill-controller', '-y', 'osa-controller') exited with status 1 ()