To solve this problem add the following code to your build gradle script

buildscript {
    repositories {
        jcenter()
        maven { url 'https://maven.google.com' }
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:3.0.0-alpha5'
        ...
    }
}

allprojects {
    repositories {
        jcenter()
        maven { url 'https://maven.google.com' }
    }
}