Error when `ionic cordova build andriod --prod --release`

#1

I got an error when use ionic cordova build andriod --prod --release.

Running app-scripts build: --prod --iscordovaserve --externalIpRequired --nobrowser

[11:54:24]  build prod started ... 
[11:54:24]  clean started ... 
[11:54:24]  clean finished in 7 ms 
[11:54:24]  copy started ... 
[11:54:24]  ngc started ... 
[WARN] Error occurred during command execution from a CLI plugin (@ionic/cli-plugin-cordova). Your plugins may be out of
       date.
Error: Type About in /Users/MyUser/Desktop/Workspace/myapp/src/pages/about/about.ts is part of the declarations of 2 modules: AppModule in /Users/MyUser/Desktop/Workspace/myapp/src/app/app.module.ts and AboutModule in /Users/MyUser/Desktop/Workspace/myapp/src/pages/about/about.module.ts! Please consider moving About in /Users/MyUser/Desktop/Workspace/myapp/src/pages/about/about.ts to a higher module that imports AppModule in /Users/MyUser/Desktop/Workspace/myapp/src/app/app.module.ts and AboutModule in /Users/MyUser/Desktop/Workspace/myapp/src/pages/about/about.module.ts. You can also create a new NgModule that exports and includes About in /Users/MyUser/Desktop/Workspace/myapp/src/pages/about/about.ts then import that NgModule in AppModule in /Users/MyUser/Desktop/Workspace/myapp/src/app/app.module.ts and AboutModule in /Users/MyUser/Desktop/Workspace/myapp/src/pages/about/about.module.ts.

Ionic info

global packages:

    @ionic/cli-utils : 1.5.0
    Cordova CLI      : 7.0.1 
    Ionic CLI        : 3.5.0

local packages:

    @ionic/app-scripts              : 2.0.0
    @ionic/cli-plugin-cordova       : 1.4.1
    @ionic/cli-plugin-ionic-angular : 1.3.2
    Cordova Platforms               : android 6.2.3
    Ionic Framework                 : ionic-angular 3.5.3

System:

    Node       : v6.11.0
    OS         : macOS Sierra
    Xcode      : Xcode 8.3.3 Build version 8E3004b 
    ios-deploy : not installed
    ios-sim    : not installed
    npm        : 3.10.10

What happen?

#2

Close, Because I found the answer about import page module.