Error:Gradle: Execution failed for task ':app:crashlyticsCleanupResourcesDebug'. > Crashlytics Developer Tools error

You need to add your API Key to the Android Manifest:

<application>
    <meta-data
        android:name="com.crashlytics.ApiKey"
        android:value="your key here" />
</application>

This method solved my problem:

Remove or Comment this line (build.gradle):

  // apply plugin: 'io.fabric'

or if you have an ApiKey, define fabric ApiKey (AndroidManifest.xml)

    <meta-data
        android:name="io.fabric.ApiKey"
        android:value="yourApiKey012356465654" />

If you only want to compose a tweet with the SDK you can remove the line

apply plugin: 'io.fabric'

And the gradle build will work correctly