Android Studio 3.0 Beta 1: Failed to resolve: com.android.support:multidex:1.0.2

Apparently my issue is I should post this:

maven {
    url 'https://maven.google.com'
}

in allprojects and not in buildscript (the subtle different has blinded me where the issue is), which then looks like this:

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

Thanks to M D for the pointers!