Running make check (on xenial) from 23-May-2017 develop I hit:
panic: Session already closed
goroutine 4323 [running]:
gopkg.in/mgo%2ev2.(*Session).cluster(0xc42065f1e0, 0xc4206e5a00)
/home/heather/work/src/gopkg.in/mgo.v2/session.go:1624 +0x81
gopkg.in/mgo%2ev2.copySession(0xc42065f1e0, 0xc4206e5b01, 0x85e502)
/home/heather/work/src/gopkg.in/mgo.v2/session.go:540 +0x40
gopkg.in/mgo%2ev2.(*Session).Copy(0xc42065f1e0, 0x2)
/home/heather/work/src/gopkg.in/mgo.v2/session.go:1590 +0x40
github.com/juju/juju/state.(*database).TransactionRunner(0xc4207eb600, 0x0, 0x0, 0x0)
/home/heather/work/src/github.com/juju/juju/state/database.go:324 +0x292
github.com/juju/juju/state.(*database).Run(0xc4207eb600, 0xc4206d0180, 0x0, 0x0)
/home/heather/work/src/github.com/juju/juju/state/database.go:378 +0x41
github.com/juju/juju/state.(*State).run(0xc42073e3c0, 0xc4206d0180, 0xc, 0x0)
/home/heather/work/src/github.com/juju/juju/state/txns.go:39 +0x3e
github.com/juju/juju/state.setStatus(0xc42073e3c0, 0x1857c68, 0x8, 0xc420b6c034, 0xc, 0x1868609, 0x12, 0x18520ef, 0x4, 0xc420cca0f0, ...)
/home/heather/work/src/github.com/juju/juju/state/status.go:123 +0x2e6
github.com/juju/juju/state.(*Machine).SetInstanceStatus(0xc4205d3200, 0x1868609, 0x12, 0x18520ef, 0x4, 0xc420cca0f0, 0xc420b5cba0, 0x0, 0x0)
/home/heather/work/src/github.com/juju/juju/state/machine.go:1007 +0x172
github.com/juju/juju/worker/provisioner_test.(*ProvisionerSuite).TestProvisionerRetriesTransientErrors.func1(0xc4203c3980, 0xc4205d3200, 0xc4207454a0)
/home/heather/work/src/github.com/juju/juju/worker/provisioner/provisioner_test.go:1292 +0x2ba
created by github.com/juju/juju/worker/provisioner_test.(*ProvisionerSuite).TestProvisionerRetriesTransientErrors
/home/heather/work/src/github.com/juju/juju/worker/provisioner/provisioner_test.go:1296 +0x4db
FAIL github.com/juju/juju/worker/provisioner 42.697s
There seems to be a similar bug, 1394223?? I was not able to reproduce it.
