title: generate signed apk is not working, apk is unsigned
body: <p>I used to generate a signed apk from Android Studio and everything was working well until I updated Android Studio to <code>3.3</code>. It generates an apk but after I try to install it, it says: App Not Installed! </p>
  
  <p>My Trial was by:</p>
  
  <ol>
  <li>Click on <code>build</code></li>
  <li>Generate Signed Apk</li>
  <li>Choose <code>APK</code> and click Next</li>
  <li>Insert the Key Store Path, Key Store Password, Key Alias, Key Password</li>
  <li>Click Next </li>
  <li>Choose Release Variant </li>
  <li>Click Finish</li>
  </ol>
  
  <p>The Apk is generated but it's not signed! What is the problem ?</p>
  
  <p><a href="https://i.stack.imgur.com/FXKie.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FXKie.png" alt="This is after trying to upload to beta"></a></p>
  
  <p>Here is my app <code>build.gradle</code></p>
  
  <pre><code>buildscript {
      repositories {
          maven { url 'https://maven.fabric.io/public' }
      }
  
      dependencies {
          classpath 'io.fabric.tools:gradle:1.+'
      }
  }
  apply plugin: 'com.android.application'
  apply plugin: 'io.fabric'
  
  repositories {
      maven { url 'https://maven.fabric.io/public' }
  }
  
  
  android {
      useLibrary 'org.apache.http.legacy'
      compileSdkVersion 27
      defaultConfig {
          applicationId "com.twobreathe.soft2breathe"
          minSdkVersion 23
          targetSdkVersion 27
          versionCode 9
          versionName "1.1"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
          externalNativeBuild {
              cmake {
                  cppFlags ""
              }
          }
          vectorDrawables {
              useSupportLibrary true
          }
          resConfigs "en", "ja"
      }
      signingConfigs {
          release {
              keyAlias "[my key alias]"
              keyPassword "[my key password]"
              storeFile file("[path to the keystore file]")
              storePassword "[my store password]"
          }
      }
  
      buildTypes {
          release {
              minifyEnabled true
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
              shrinkResources true
              pseudoLocalesEnabled false
          }
  
          debug {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
              debuggable true
          }
  
  
      }
      externalNativeBuild {
          cmake {
              path "src/main/cpp/fluidsynth/android/CMakeLists.txt"
          }
      }
      lintOptions {
          checkReleaseBuilds false
          abortOnError false
      }
      dataBinding {
          enabled true
      }
      compileOptions {
          sourceCompatibility JavaVersion.VERSION_1_8
          targetCompatibility JavaVersion.VERSION_1_8
      }
      buildToolsVersion '28.0.3'
      productFlavors {
      }
  }
  
  dependencies {
      implementation fileTree(include: ['*.jar'], dir: 'libs')
      implementation 'com.android.support:appcompat-v7:27.1.1'
      implementation 'com.android.support.constraint:constraint-layout:1.1.3'
      implementation 'com.github.parse-community.Parse-SDK-Android:parse:1.18.4'
      implementation 'com.jjoe64:graphview:4.2.2'
      implementation 'io.reactivex.rxjava2:rxjava:2.2.0'
      implementation 'io.reactivex.rxjava2:rxandroid:2.1.0'
      testImplementation 'junit:junit:4.12'
      implementation 'com.orhanobut:hawk:2.0.1'
      implementation 'xyz.sahildave:arclayout:1.0.0'
      implementation 'com.mikhaellopez:circularprogressbar:2.0.0'
      androidTestImplementation 'com.android.support.test:runner:1.0.2'
      implementation 'com.github.GrenderG:Toasty:1.3.0'
      implementation 'com.kyleduo.switchbutton:library:2.0.0'
      implementation 'com.github.franmontiel:LocaleChanger:0.9.2'
      implementation 'cn.aigestudio.wheelpicker:WheelPicker:1.1.2'
      androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
      implementation 'com.crashlytics.sdk.android:crashlytics:2.9.8'
  }
  </code></pre>