bundleRelease has been changed to bundleReleaseAar in Android Gradle Plugin 3.3.x. This is used in the bottom of library’s build.gradle file.

publishing {
    publications {
      library(MavenPublication) {
        setGroupId(groupId)
        setArtifactId(artifactId)
        version android.defaultConfig.versionName

        artifact(bundleReleaseAar)
      }
    }