title: Flutter Build error : Execution failed for task ':app:checkDebugAarMetadata'
body: <p>I get the below build exception when I try to run my app.I use onesignal_flutter package for email, sms, push notification, and in-app message service.</p>
  <pre><code>BUILD FAILED in 7s
  Running Gradle task 'assembleDebug'...
  [!] Gradle threw an error while downloading artifacts from the network. Retrying to 
  download...
  
  FAILURE: Build failed with an exception.
  
  * What went wrong:
  Execution failed for task ':app:checkDebugAarMetadata'.
  &gt; Could not resolve all files for configuration ':app:debugRuntimeClasspath'.
  &gt; Could not resolve com.onesignal:OneSignal:[3.11.2, 3.99.99].
   Required by:
       project :app
    &gt; Failed to list versions for com.onesignal:OneSignal.
       &gt; Unable to load Maven meta-data from 
  https://google.bintray.com/exoplayer/com/onesignal/OneSignal/maven-metadata.xml.
          &gt; Could not get resource 
  'https://google.bintray.com/exoplayer/com/onesignal/OneSignal/maven-metadata.xml'.
             &gt; Could not GET 
  'https://google.bintray.com/exoplayer/com/onesignal/OneSignal/maven-metadata.xml'. 
  Received status code 502 from server: Bad Gateway
  
   * Try:
   Run with --stacktrace option to get the stack trace. Run with --info or --debug option 
   to 
   get more log output. Run with --scan to get full insights.
  
   * Get more help at https://help.gradle.org
  
  BUILD FAILED in 6s
  [!] Gradle threw an error while downloading artifacts from the network. Retrying to 
  download...
  Exception: Gradle task assembleDebug failed with exit code 1
  </code></pre>
  <p>Any kind of help would be great</p>