I'm seeing lots of "Skipping change xxx because the corresponding repository was not found" at https://gerrit.wikimedia.org/r/monitoring
For example:
```
com.google.gerrit.server.permissions.PermissionBackendException: project 'maps/tilerator' is unavailable
at com.google.gerrit.server.permissions.FailedPermissionBackend$FailedChange.test(FailedPermissionBackend.java:170)
at com.google.gerrit.server.permissions.PermissionBackend$ForChange.test(PermissionBackend.java:383)
at com.google.gerrit.server.query.change.ChangeIsVisibleToPredicate.match(ChangeIsVisibleToPredicate.java:70)
at com.google.gerrit.server.query.change.ChangeIsVisibleToPredicate.match(ChangeIsVisibleToPredicate.java:32)
at com.google.gerrit.index.query.AndSource.match(AndSource.java:147)
at com.google.gerrit.index.query.AndSource.readImpl(AndSource.java:101)
at com.google.gerrit.index.query.AndSource.read(AndSource.java:83)
at com.google.gerrit.index.query.QueryProcessor.query(QueryProcessor.java:238)
at com.google.gerrit.index.query.QueryProcessor.query(QueryProcessor.java:174)
at com.google.gerrit.index.query.QueryProcessor.query(QueryProcessor.java:157)
at com.google.gerrit.server.query.change.OutputStreamQuery.query(OutputStreamQuery.java:201)
at com.google.gerrit.sshd.commands.Query.run(Query.java:103)
at com.google.gerrit.sshd.SshCommand$1.run(SshCommand.java:36)
at com.google.gerrit.sshd.BaseCommand$TaskThunk.run(BaseCommand.java:459)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at com.google.gerrit.server.git.WorkQueue$Task.run(WorkQueue.java:558)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.eclipse.jgit.errors.RepositoryNotFoundException: repository not found: /srv/gerrit/git/maps/tilerator
at com.google.gerrit.server.git.LocalDiskRepositoryManager.openRepository(LocalDiskRepositoryManager.java:157)
at com.google.gerrit.server.git.LocalDiskRepositoryManager.openRepository(LocalDiskRepositoryManager.java:139)
at com.google.gerrit.server.project.ProjectCacheImpl$Loader.load(ProjectCacheImpl.java:310)
at com.google.gerrit.server.project.ProjectCacheImpl$Loader.load(ProjectCacheImpl.java:294)
at com.google.common.cache.LocalCache$LoadingValueReference.loadFuture(LocalCache.java:3524)
at com.google.common.cache.LocalCache$Segment.loadSync(LocalCache.java:2273)
at com.google.common.cache.LocalCache$Segment.lockedGetOrLoad(LocalCache.java:2156)
at com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2046)
at com.google.common.cache.LocalCache.get(LocalCache.java:3943)
at com.google.common.cache.LocalCache.getOrLoad(LocalCache.java:3967)
at com.google.common.cache.LocalCache$LocalLoadingCache.get(LocalCache.java:4952)
at com.google.gerrit.server.project.ProjectCacheImpl.strictCheckedGet(ProjectCacheImpl.java:161)
at com.google.gerrit.server.project.ProjectCacheImpl.checkedGet(ProjectCacheImpl.java:157)
at com.google.gerrit.server.project.DefaultPermissionBackend$WithUserImpl.project(DefaultPermissionBackend.java:73)
at com.google.gerrit.server.permissions.PermissionBackend$WithUser.ref(PermissionBackend.java:145)
at com.google.gerrit.server.permissions.PermissionBackend$WithUser.indexedChange(PermissionBackend.java:168)
at com.google.gerrit.server.query.change.ChangeIsVisibleToPredicate.match(ChangeIsVisibleToPredicate.java:68)
... 19 more
```
and many more.
This is likley because of the index (which means the delete-project plugin didn't reindex after?)