Error generating an APK in Android Studio

Trying to generate a BUILD APK shows me the following error

  

Build APK: Errors while building APK. You can find the errors   in the 'Messages' view.

He tells me that I have errors in the messages I do not understand what he means by this. Any idea how to fix it?

My Build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.3"

    defaultConfig {
        applicationId "com.example.hp14.iteracion2"
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
        // Enabling multidex support.
        multiDexEnabled true
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }


}

dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    compile files('libs/volley.jar')
    compile 'com.android.support:appcompat-v7:23.3.0'
    compile 'com.android.support:design:23.3.0'
    compile 'com.android.support:support-v4:23.3.0'
    compile 'com.loopj.android:android-async-http:1.4.9'
    compile 'com.google.android.gms:play-services:8.4.0'
    testCompile 'junit:junit:4.12'
    compile files('libs/glide-3.7.0.jar')
    compile 'com.android.support:recyclerview-v7:23.3.0'
    compile 'com.android.support:cardview-v7:23.3.0'
}