Scaffolding add-on failed to enable if Comala Workflow is already installed in Confluence

Summary

In atlassian-confluence.log you would see the following error:

2017-08-16 14:32:05,046 ERROR [ThreadPoolAsyncTaskExecutor::Thread 46] [atlassian.plugin.module.PrefixDelegatingModuleFactory] createModule Detected an error (NoClassDefFoundError) instantiating the module for plugin 'com.comalatech.workflow' for module 'workflowSupplier': com/servicerocket/confluence/randombits/supplier/core/annotate/AnnotatedSupplier.  
2017-08-16 14:32:05,274 ERROR [ThreadPoolAsyncTaskExecutor::Thread 46] [plugin.osgi.factory.OsgiPlugin] onPluginContainerFailed Unable to start the plugin container for plugin 'com.servicerocket.confluence.plugin.servicerocket-utility-library'

Subsequently, ServiceRocket Utility Library add-on would fail to enable as well.

Workaround

We're still investigating this matter however to workaround this issue, you could follow these steps:

Uninstall Comala Workflow, Scaffolding add-on & ServiceRocket Utility Library add-on
Install Scaffolding add-on first which will also install ServiceRocket Utility Library add-on
Then, install Comala Workflow

The problem will not happen if ServiceRocket Utility Library add-on already exists on the server prior to Scaffolding add-on installation.