Import errors into Android app after upgrading to Gradle 2.3.0

I have an Android application on Android Studio that includes the following two import statements:

import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.extensions.android.json.AndroidJsonFactory;

      

        
        
        
      

    

I have no problem with these imports when using Gradle plugin version 2.2.3. However, after upgrading to Gradle plugin 2.3.1, the instructions show errors: "extensions" turn red in both cases, and the error says "can't resolve extensions".

Here's some up-to-date background information:

Android Studio version 2.3.1

Gradle version 3.3

CompileSDKVersion 25

buildToolsVersion '25 .0.0 '

Android SDK Tools Version 26.0.1

I reported this as a bug to Google, but wondered if anyone else had similar issues or might be thinking of a possible explanation?

    dependencies {
        compile fileTree(include: ['*.jar'], dir: 'libs')
        compile project(path: ':backend', configuration: 'android-endpoints')
        compile 'com.android.support:appcompat-v7:25.2.0'
        compile 'com.android.support:support-v4:25.2.0'
        compile 'com.android.support:recyclerview-v7:25.2.0'
        compile 'com.android.support:design:25.2.0'
        compile 'com.android.support:percent:25.2.0'
        compile 'com.google.firebase:firebase-database:10.2.0'
        compile 'com.google.firebase:firebase-core:10.2.0'
        compile 'com.google.firebase:firebase-messaging:10.2.0'
        compile 'com.firebaseui:firebase-ui-database:1.0.1'
        compile 'com.fasterxml.jackson.core:jackson-annotations:2.8.0.rc2'
        compile 'com.google.code.findbugs:jsr305:2.0.1'
        compile 'com.android.support.constraint:constraint-layout:1.0.2'
        testCompile 'junit:junit:4.12'
}