Can happen if activation is not setup properly, or even absent.

Suggesting to warn on install context instead, e.g.

Skipping subscription setup for workspace imaging, activation module is not installed.

Ideally, subscription gets out of SetupModuleRepositoriesTask at some point, in favor of a default mechanism.

Update 2017.03.27:
We give a shot at splitting the SMRTask into 3 subtasks for a. repo init, b. granting perms and c. setting up subscribers (time-box to 3). Namely we try to make an ArrayDelegateTask out of that.

Update 2017.04.11:

Step to reproduce:

• Remove magnolia-module-activation dependency in empty-webapp pom
• Add <optional>true</optional> in any dependency to activation in module descriptor of imaging, pages, resources
• Run fresh install empty-webapp
• Observe error log:

  17-04-11 09:44:43,953 ERROR info.magnolia.module.InstallContextImpl           : [101/371 tasks - Magnolia Imaging Module (version 3.3.2-SNAPSHOT)]> Could not install or update imaging module. Task 'Setup module repositories' failed. (NullPointerException: )
  info.magnolia.module.delta.TaskExecutionException: Could not bootstrap workspace: null
  	at info.magnolia.module.delta.SetupModuleRepositoriesTask.execute(SetupModuleRepositoriesTask.java:91)
  	at info.magnolia.module.ModuleManagerImpl.applyDeltas(ModuleManagerImpl.java:545)
  	at info.magnolia.module.ModuleManagerImpl.installOrUpdateModule(ModuleManagerImpl.java:527)
  	at info.magnolia.module.ModuleManagerImpl$1.doExec(ModuleManagerImpl.java:302)
  	at info.magnolia.context.MgnlContext$VoidOp.exec(MgnlContext.java:429)
  	at info.magnolia.context.MgnlContext$VoidOp.exec(MgnlContext.java:426)
  	at info.magnolia.context.MgnlContext.doInSystemContext(MgnlContext.java:400)
  	at info.magnolia.module.ModuleManagerImpl.performInstallOrUpdate(ModuleManagerImpl.java:296)
  	at info.magnolia.module.ui.ModuleManagerWebUI$2.run(ModuleManagerWebUI.java:126)
  	at java.lang.Thread.run(Thread.java:745)
  Caused by: java.lang.NullPointerException
  	at info.magnolia.module.delta.SetupModuleRepositoriesTask.subscribeRepository(SetupModuleRepositoriesTask.java:109)
  	at info.magnolia.module.delta.SetupModuleRepositoriesTask.execute(SetupModuleRepositoriesTask.java:87)
  	... 9 more