title: Extension of type 'BintrayExtension' does not exist
body: <p>My project <code>build.gradle</code>:</p>
  
  <pre><code>...
  plugins {
      id "maven-publish"
      id "com.jfrog.bintray" version "1.8.5"
  }
  </code></pre>
  
  <p>My library module <code>build.gradle</code>:</p>
  
  <pre><code>apply plugin: 'kotlin'
  apply plugin: 'java-library'
  apply plugin: 'com.android.lint'
  ...
  if (project.rootProject.file('local.properties').exists()) {
      apply from: rootProject.file('deploy-bintray.gradle.kts')
  }
  </code></pre>
  
  <p>My library module <code>deploy-bintray.gradle.kts</code>:</p>
  
  <pre><code>import com.jfrog.bintray.gradle.BintrayExtension
  
  apply(plugin = "maven-publish")
  apply(plugin = "com.jfrog.bintray")
  
  configure&lt;BintrayExtension&gt; {...}
  configure&lt;PublishingExtension&gt; {...}
  </code></pre>
  
  <p>And this is the error I get from <code>gradle assemble</code>:</p>
  
  <blockquote>
    <p>Extension of type 'BintrayExtension' does not exist. Currently registered extension types: [ExtraPropertiesExtension,
    KotlinJvmProjectExtension, KotlinTestsRegistry,
    DefaultArtifactPublicationSet, ReportingExtension, SourceSetContainer,
    JavaPluginExtension, JavaInstallationRegistry, LintOptions,
    PublishingExtension, BintrayExtension]</p>
  </blockquote>
  
  <p>I've added:</p>
  
  <pre><code>buildscript {
      repositories {
          maven("https://plugins.gradle.org/m2")
      }
  
      dependencies {
          classpath("com.jfrog.bintray.gradle:gradle-bintray-plugin:1.8.5")
      }
  }
  </code></pre>
  
  <p>But I get the same output... If I open <code>BintrayExtension.groovy</code> the package name <code>com.jfrog.bintray.gradle</code> has this warning: </p>
  
  <blockquote>
    <p>Package name mismatch. Actual: 'com.jfrog.bintray.gradle', expected:
    ''</p>
  </blockquote>
  
  <p>and the class:</p>
  
  <blockquote>
    <p>Class 'BintrayExtension' already exists in 'com.jfrog.bintray.gradle'</p>
  </blockquote>
  
  <p>What am I missing here?</p>