Error:(1, 0) Plugin is too old, please update to a more recent version, or set ANDROID_DAILY_OVERRID

今天从Eclipse切换Android Studio工程时，报了个奇葩错误：

Error:(1, 0) Plugin is too old, please update to a more recent version, or set ANDROID_DAILY_OVERRIDE environment variab

找了半天也没找到什么原因，把原来的好的工程拿出来看了看，替换了Project下的build.gradle文件，就好了，然后比较新旧两个文件，原来是这里不一样：
旧文件（可以运行的）

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        jcenter()

    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.2.3'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

新文件（不可以运行的：）

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.0.0-alpha1'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

原来是classpath升级了，导致的问题！换回原来的就好了