I follow steps from https://docs.sencha.com/extjs/6.7.0-...ha_ExtGen.html to create new application.
And got error on ext-gen app -a step

E:\WORKSPACES\ext>ext-gen app -a

Sencha ExtGen v6.7.0 Community Edition - The Ext JS code generator

Defaults for Ext JS app:
appName:        MyExtGenApp
template:       moderndesktop
modernTheme:    theme-material

Defaults for package.json:
packageName:    my-app
version:        0.0.1
description:    my-ext-gen-app description for Ext JS app MyExtGenApp
repositoryURL:  https://github.com/
keywords:       "Ext JS","Sencha","HTML5"
authorName:     Sencha, Inc.
license:        ISC
bugsURL:        https://github.com/
homepageURL:    http://www.sencha.com

i [ext]: ext-gen: E:\WORKSPACES\ext/my-app created
i [ext]: ext-gen: package.json created for my-app
i [ext]: ext-gen: webpack.config.js created for my-app
i [ext]: ext-gen: npm install -s started for my-app
i [ext]: ext-gen: npm install -s completed for my-app
(node:11000) UnhandledPromiseRejectionWarning: Error: Cannot find module 'E:\WORKSPACES\ext\my-app\node_modules\@sencha\ext\package.json'
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:582:15)
    at Function.Module._load (internal/modules/cjs/loader.js:508:25)
    at Module.require (internal/modules/cjs/loader.js:637:17)
    at require (internal/modules/cjs/helpers.js:22:18)
    at stepCreate (C:\Users\Yura\AppData\Roaming\npm\node_modules\@sencha\ext-gen\ext-gen.js:606:22)
    at process._tickCallback (internal/process/next_tick.js:68:7)
(node:11000) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:11000) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.