gradle更新 build:gradle出错

Error:Could not find com.android.tools.build:gradle:3.0.0-alpha1.
Searched in the following locations:
file:/D:/Android/android-studio3.0/gradle/m2repository/com/android/tools/build/gradle/3.0.0-alpha1/gradle-3.0.0-alpha1.pom
file:/D:/Android/android-studio3.0/gradle/m2repository/com/android/tools/build/gradle/3.0.0-alpha1/gradle-3.0.0-alpha1.jar
https://jcenter.bintray.com/com/android/tools/build/gradle/3.0.0-alpha1/gradle-3.0.0-alpha1.pom
https://jcenter.bintray.com/com/android/tools/build/gradle/3.0.0-alpha1/gradle-3.0.0-alpha1.jar
Required by:
project :

  buildscript {
repositories {
    jcenter()
    google()  //添加这个
}
dependencies {
    classpath 'com.android.tools.build:gradle:3.0.0-alpha8'
   // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files
}}