enforcing dependency convergence

pom.xml

<?xml version="1.0" encoding="utf-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>test</groupId>
  <artifactId>enforcer-dependency-convergence-test</artifactId>
  <version>0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
  <dependencies>
    <dependency>
      <groupId>ch.qos.logback</groupId>
      <artifactId>logback-classic</artifactId>
      <version>1.1.3</version> <!-- depends on slf4j-api:1.7.7 -->
      <scope>runtime</scope>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>log4j-over-slf4j</artifactId>
      <version>${unified.slf4j-api.version}</version>
      <scope>runtime</scope>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>${unified.slf4j-api.version}</version>
    </dependency>
  </dependencies>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <unified.slf4j-api.version>1.7.7</unified.slf4j-api.version>
  </properties>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>1.4.1</version>
        <executions>
          <execution>
            <goals>
              <goal>enforce</goal>
            </goals>
            <configuration>
              <rules>
                <dependencyConvergence/>
              </rules>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>