Tools build error in Gradle file, Android Studio

I recently changed the application's versionName and versionCode, and so far that is the only thing I did when I started Android Studio, and I try to sync and the error appears. The error is:

Error:Could not find any version that matches com.android.tools.build:gradle:0.12.+.
Required by:
    :Lajerganadsat:unspecified

Here is the content of the Gradle file:

apply plugin: 'com.android.application'

android {
    compileSdkVersion 21
    buildToolsVersion "21.1.1"

    defaultConfig {
        applicationId "nadsat.aplicacion.safrapp.lajerganadsat"
        minSdkVersion 9
        targetSdkVersion 21
        versionCode 9
        versionName "1.0.8"
    }
    buildTypes {
        release {
            runProguard false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:21.0.0'
    compile 'com.google.android.gms:play-services:6.+'
}