title: Gradle fails to resolve spring dependency
body: <p>I am trying to build my project with the following <code>build.gradle</code> file.</p>
  <pre><code>buildscript {
      repositories {
          mavenCentral()
      }
      dependencies {
          classpath('org.springframework.boot:spring-boot-gradle-plugin:1.2.1.RELEASE')
      }
  }
  
  apply plugin: 'java'
  apply plugin: 'idea'
  apply plugin: 'spring-boot'
  
  repositories {
      maven {
          url 'https://repo.spring.io/milestone'
      }
      mavenCentral()
  }
  
  dependencies {
      compile('org.springframework.boot:spring-boot-starter-web')
      compile('org.springframework.boot:spring-boot-starter-data-mongodb:1.2.2.RELEASE')
      compile('org.springframework.data:spring-data-mongodb:1.7.0.RC1')
  
      compile('org.springframework.cloud:spring-cloud-spring-service-connector')
      compile('org.springframework.cloud:spring-cloud-cloudfoundry-connector')
  
      compile 'org.springframework:spring-test:4.1.5.RELEASE'
      compile 'de.grundid.opendatalab:geojson-jackson:1.3'
      compile 'com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.5.1'
      compile 'org.apache.httpcomponents:httpclient:4.4'
  
      testCompile('junit:junit')
  }
  
  task wrapper(type: Wrapper) {
      gradleVersion = '2.3'
  }
  </code></pre>
  <p>I added the milestone repository because I need the spring-data-mongodb 1.7.0.RC1 dependency. However, there seems to be something wrong with the references of the parent-poms because gradle is unable to fetch the following dependency: <code>org.springframework.data.build:spring-data-parent:1.6.0.RC1</code></p>
  <p>It exits with the following error:</p>
  <pre><code>Could not find org.springframework.data.build:spring-data-parent:1.6.0.RC1.
  Searched in the following locations:
      https://repo.spring.io/milestone/org/springframework/data/build/spring-data-parent/1.6.0.RC1/spring-data-parent-1.6.0.RC1.pom
      https://repo.spring.io/milestone/org/springframework/data/build/spring-data-parent/1.6.0.RC1/spring-data-parent-1.6.0.RC1.jar
      https://repo1.maven.org/maven2/org/springframework/data/build/spring-data-parent/1.6.0.RC1/spring-data-parent-1.6.0.RC1.pom
      https://repo1.maven.org/maven2/org/springframework/data/build/spring-data-parent/1.6.0.RC1/spring-data-parent-1.6.0.RC1.jar
  </code></pre>
  <p>The output of the <code>gradlew build --debug</code> command can be found here: <a href="http://pastebin.com/seYRMFQP" rel="nofollow noreferrer">http://pastebin.com/seYRMFQP</a></p>
  <p>The command additionally produced the following output to stdout: <a href="http://pastebin.com/atcWQsKF" rel="nofollow noreferrer">http://pastebin.com/atcWQsKF</a></p>
  <p>I already tried to clean my local gradle cache but it did not resolve the problem.</p>