title: Plugin [id: 'com.github.ben-manes.versions'] was not found in any of the following sources
body: <p>Here is my gradle build file and getting the following error:- </p>
  
  <pre><code>/*
   * This file was generated by the Gradle 'init' task.
   *
   * This generated file contains a sample Java Library project to get you started.
   * For more details take a look at the Java Libraries chapter in the Gradle
   * user guide available at https://docs.gradle.org/4.10.2/userguide/java_library_plugin.html
   */
  
  plugins {
      // Apply the java-library plugin to add support for Java Library
      id 'java-library'
      id 'de.fuerstenau.buildconfig' version '1.1.8' apply true
      id 'eclipse'
      id 'com.github.ben-manes.versions' version '$version'
      id 'com.palantir.git-version'
  }
  
  dependencies {
      classpath(
          "gradle.plugin.com.palantir.gradle.gitversion:gradle-git-version:0.5.3",
          "com.github.ben-manes:gradle-versions-plugin:0.13.0",
          "gradle.plugin.de.fuerstenau:BuildConfigPlugin:1.1.4",
          "net.ltgt.gradle:gradle-apt-plugin:0.13",
          "com.jfrog.bintray.gradle:gradle-bintray-plugin:1.7.3",
       )
      compile(
        "com.squareup.okhttp3:okhttp:$versions.okhttp",
        "com.google.code.gson:gson:$versions.gson",
      )
  
      compileOnly(
        "com.google.auto.value:auto-value:$versions.autoValue",
        deps.nullityAnnotations,
        "com.github.kevinmost.auto-value-custom-hashcode-equals:adapter:$versions.customHashCodeEquals",
          )
  
      apt(
        "com.google.auto.value:auto-value:$versions.autoValue",
        "com.gabrielittner.auto.value:auto-value-with:1.0.0",
        "com.github.kevinmost.auto-value-custom-hashcode-equals:processor:$versions.customHashCodeEquals",
      )
  
      // This dependency is exported to consumers, that is to say found on their compile classpath.
      api 'org.apache.commons:commons-math3:3.6.1'
  
      // This dependency is used internally, and not exposed to consumers on their own compile classpath.
      implementation 'com.google.guava:guava:23.0'
  
      // Use JUnit test framework
      testImplementation 'junit:junit:4.12'
  }
  
  // In this section you declare where to find the dependencies of your project
  repositories {
      // Use jcenter for resolving your dependencies.
      // You can declare any Maven/Ivy/file repository here.
      jcenter()
      mavenLocal()    
      mavenCentral()
      maven { url "https://jitpack.io" }
  }
  
  buildConfig {
    packageName = "api2"
    clsName = "BuildConfig"
  }
  
   ext.versions = [
        okhttp: "3.4.1",
        gson: "2.7",
        autoValue: "1.5.2",
        slf4j: "1.7.21",
        kotlin: "1.0.5-2",
  
        customHashCodeEquals: "db3442d",
    ]
  </code></pre>
  
  <p>Error:_</p>
  
  <pre><code>* What went wrong:
  Plugin [id: 'com.github.ben-manes.versions'] was not found in any of the following sources:
  
  - Gradle Core Plugins (plugin is not in 'org.gradle' namespace)
  - Plugin Repositories (plugin dependency must include a version number for this source)
  </code></pre>