I've seen another intermittent TestUniterRelations failure, which I'm adding under this bug because they might both be related:

test 5: unit becomes dead while in a relation

step 0:

uniter_test.quickStartRelation{}
uniter_test.quickStart{}
uniter_test.createCharm{revision:0, badHooks:[]string(nil), customize:(func(*gocheck.C, *uniter_test.context, string))(nil)}
uniter_test.addCharm{dir:(*charm.Dir)(0xc21026aea0), curl:(*charm.URL)(0xc210732a00)}
uniter_test.serveCharm{}
uniter_test.createUniter{}
uniter_test.ensureStateWorker{}
uniter_test.createServiceAndUnit{serviceName:""}
API: login as "unit-u-0" successful
uniter_test.startUniter{unitTag:""}
uniter_test.waitAddresses{}
uniter_test.waitUnit{status:"started", info:"", data:params.StatusData(nil), charm:0, resolved:""}
want unit status "started", got "pending"; still waiting
want unit status "started", got "pending"; still waiting
want unit status "started", got "pending"; still waiting
want unit status "started", got "installed"; still waiting
want unit status "started", got "installed"; still waiting
uniter_test.waitHooks{"install", "config-changed", "start"}
waiting for hooks: []string{"install", "config-changed", "start"}
ctx.hooksCompleted: []string{"install", "config-changed", "start"}
uniter_test.verifyCharm{revision:0, dirty:false}
uniter_test.waitHooks{}
waiting for hooks: []string{"install", "config-changed", "start"}
ctx.hooksCompleted: []string{"install", "config-changed", "start"}
uniter_test.addRelation{waitJoin:false}
uniter_test.addRelationUnit{}
uniter_test.waitHooks{"db-relation-joined mysql/0 db:0", "db-relation-changed mysql/0 db:0"}
waiting for hooks: []string{"install", "config-changed", "start", "db-relation-joined mysql/0 db:0", "db-relation-changed mysql/0 db:0"}
ctx.hooksCompleted: []string{"install", "config-changed", "start"}
ctx.hooksCompleted: []string{"install", "config-changed", "start"}
ctx.hooksCompleted: []string{"install", "config-changed", "start", "db-relation-joined mysql/0 db:0"}
ctx.hooksCompleted: []string{"install", "config-changed", "start", "db-relation-joined mysql/0 db:0", "db-relation-changed mysql/0 db:0"}
uniter_test.verifyRunning{noHooks:false}
uniter_test.stopUniter{err:""}
uniter_test.startUniter{unitTag:""}
uniter_test.waitHooks{"config-changed"}
waiting for hooks: []string{"install", "config-changed", "start", "db-relation-joined mysql/0 db:0", "db-relation-changed mysql/0 db:0", "config-changed"}
ctx.hooksCompleted: []string{"install", "config-changed", "start", "db-relation-joined mysql/0 db:0", "db-relation-changed mysql/0 db:0"}
ctx.hooksCompleted: []string{"install", "config-changed", "start", "db-relation-joined mysql/0 db:0", "db-relation-changed mysql/0 db:0"}
ctx.hooksCompleted: []string{"install", "config-changed", "start", "db-relation-joined mysql/0 db:0", "db-relation-changed mysql/0 db:0", "config-changed"}
step 1:

uniter_test.custom{f:(func(*gocheck.C, *uniter_test.context))(0x45d290)}
step 2:

uniter_test.waitUniterDead{err:""}
uniter_test.startUniter{unitTag:""}
uniter_test.go:1026:
    s.runUniterTests(c, relationsTests)
uniter_test.go:1392:
    c.Assert(err, gc.Equals, worker.ErrTerminateAgent)
... obtained *errors.errorString = &errors.errorString{s:"failed to initialize uniter for \"unit-u-0\": agent should be terminated"} ("failed to initialize uniter for \"unit-u-0\": agent should be terminated")
... expected *errors.errorString = &errors.errorString{s:"agent should be terminated"} ("agent should be terminated")