Following advice from here:
here: https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md
and here: https://www.npmjs.com/package/generator-kibana-plugin
Generated base plugin from the base yeoman, and can't start Kibana without getting this error, when my plugin is in place:
FATAL [TypeError: Cannot read property 'error' of undefined]
server    log   [13:37:57.478] [fatal] TypeError: Cannot read property 'error' of undefined
    at OptionManager.mergeOptions (/Users/jay/Workspace/kibana/node_modules/babel-core/lib/transformation/file/options/option-manager.js:126:28)
    at OptionManager.addConfig (/Users/jay/Workspace/kibana/node_modules/babel-core/lib/transformation/file/options/option-manager.js:107:10)
    at OptionManager.findConfigs (/Users/jay/Workspace/kibana/node_modules/babel-core/lib/transformation/file/options/option-manager.js:168:35)
    at OptionManager.init (/Users/jay/Workspace/kibana/node_modules/babel-core/lib/transformation/file/options/option-manager.js:229:12)
    at compile (/Users/jay/Workspace/kibana/node_modules/babel-core/lib/api/register/node.js:117:22)
    at normalLoader (/Users/jay/Workspace/kibana/node_modules/babel-core/lib/api/register/node.js:199:14)
    at Object.require.extensions.(anonymous function) [as .js] (/Users/jay/Workspace/kibana/node_modules/babel-core/lib/api/register/node.js:216:7)
    at Module.load (module.js:344:32)
    at Function.Module._load (module.js:301:12)
    at Module.require (module.js:354:17)
    at require (internal/module.js:12:17)
    at Plugins._new$ (/Users/jay/Workspace/kibana/src/server/plugins/PluginCollection.js:22:28)
    at tryCatch (/Users/jay/Workspace/kibana/node_modules/babel-runtime/regenerator/runtime.js:67:40)
    at GeneratorFunctionPrototype.invoke [as _invoke] (/Users/jay/Workspace/kibana/node_modules/babel-runtime/regenerator/runtime.js:315:22)
    at GeneratorFunctionPrototype.prototype.(anonymous function) [as next] (/Users/jay/Workspace/kibana/node_modules/babel-runtime/regenerator/runtime.js:100:21)
    at invoke (/Users/jay/Workspace/kibana/node_modules/babel-runtime/regenerator/runtime.js:136:37)
FATAL [TypeError: Cannot read property 'error' of undefined]
 optimizer crashed  with status code 1