We've started to see a frequent and disruptive occurrence of this in OpenStack CI, using Juju 1.25.6.

The juju status shows unit's agent-state as 'failed', and inspection of the unit's machine log show sha256 mismatch in retrieving the charm from the controller.

A few examples with artifacts and logs (we have a lot more available if needed):

https://openstack-ci-reports.ubuntu.com/artifacts/test_charm_pipeline_amulet_full/openstack/charm-nova-cloud-controller/375028/11/146/index.html

https://openstack-ci-reports.ubuntu.com/artifacts/test_charm_pipeline_amulet_full/openstack/charm-ceph/375009/14/189/index.html

https://openstack-ci-reports.ubuntu.com/artifacts/test_charm_pipeline_amulet_full/openstack/charm-swift-proxy/375035/11/173/index.html


2016-10-07 23:11:48 INFO juju.worker.uniter modes.go:567 ModeContinue starting
2016-10-07 23:11:48 INFO juju.worker.uniter modes.go:59 resuming charm install
2016-10-07 23:11:48 INFO juju.worker.uniter modes.go:569 ModeContinue exiting
2016-10-07 23:11:48 INFO juju.worker.uniter modes.go:567 ModeInstalling local:trusty/nova-cloud-controller-501 starting
2016-10-07 23:11:48 INFO juju.worker.uniter.operation executor.go:69 running operation install local:trusty/nova-cloud-controller-501
2016-10-07 23:11:48 INFO juju.worker.uniter.operation executor.go:103 preparing operation "install local:trusty/nova-cloud-controller-501"
2016-10-07 23:11:48 INFO juju.worker.uniter.charm bundles.go:60 downloading local:trusty/nova-cloud-controller-501 from https://172.17.100.7:17070/environment/9dca5c31-16ed-437f-875e-e07c3452f4e5/charms?file=%2A&url=local%3Atrusty%2Fnova-cloud-controller-501
2016-10-07 23:11:48 DEBUG juju.worker.uniter.filter filter.go:461 got address change
2016-10-07 23:11:48 DEBUG juju.worker.uniter.filter filter.go:422 no config change seen yet, skipping config event
2016-10-07 23:11:48 DEBUG juju.worker.uniter.filter filter.go:502 got storage change
2016-10-07 23:11:48 DEBUG juju.worker.uniter.filter filter.go:438 got unit change
2016-10-07 23:11:48 DEBUG juju.worker.uniter.filter filter.go:446 got service change
2016-10-07 23:11:48 DEBUG juju.worker.uniter.filter filter.go:717 charm check skipped, not yet installed.
2016-10-07 23:11:48 INFO juju.worker.uniter.charm bundles.go:69 download complete
2016-10-07 23:11:48 DEBUG juju.worker.uniter modes.go:31 [AGENT-STATUS] failed: install local:trusty/nova-cloud-controller-501
2016-10-07 23:11:48 INFO juju.worker.uniter modes.go:569 ModeInstalling local:trusty/nova-cloud-controller-501 exiting
2016-10-07 23:11:48 INFO juju.worker.uniter uniter.go:203 unit "nova-cloud-controller/1" shutting down: ModeInstalling local:trusty/nova-cloud-controller-501: preparing operation "install local:trusty/nova-cloud-controller-501": failed to download charm "local:trusty/nova-cloud-controller-501" from ["https://172.17.100.7:17070/environment/9dca5c31-16ed-437f-875e-e07c3452f4e5/charms?file=%2A&url=local%3Atrusty%2Fnova-cloud-controller-501"]: expected sha256 "d1d568bab3374bb76a0026a61f860b96be257daf44cef8cf6c7f7e63f5509ca4", got "c810a99450727181f0f9384de313ec6e18567c1d3a0b0f1ec86c2abfbc076c2e"
2016-10-07 23:11:48 DEBUG juju.worker.uniter runlistener.go:109 juju-run listener stopping
2016-10-07 23:11:48 DEBUG juju.worker.uniter runlistener.go:129 juju-run listener stopped
2016-10-07 23:11:48 ERROR juju.worker.uniter.filter filter.go:137 tomb: dying
2016-10-07 23:11:48 INFO juju.worker.dependency engine.go:351 "uniter" manifold worker stopped: ModeInstalling local:trusty/nova-cloud-controller-501: preparing operation "install local:trusty/nova-cloud-controller-501": failed to download charm "local:trusty/nova-cloud-controller-501" from ["https://172.17.100.7:17070/environment/9dca5c31-16ed-437f-875e-e07c3452f4e5/charms?file=%2A&url=local%3Atrusty%2Fnova-cloud-controller-501"]: expected sha256 "d1d568bab3374bb76a0026a61f860b96be257daf44cef8cf6c7f7e63f5509ca4", got "c810a99450727181f0f9384de313ec6e18567c1d3a0b0f1ec86c2abfbc076c2e"
2016-10-07 23:11:48 DEBUG juju.worker.dependency engine.go:443 restarting dependents of "uniter" manifold
2016-10-07 23:11:48 INFO juju.worker.dependency engine.go:293 starting "uniter" manifold worker in 3s...