title: ClassNotFoundException in maven-archetype-plugin
body: <p>I'm using Apache Maven 3.6.1 to generate a project from an archetype. </p>
  
  <p>While the <code>mvn org.apache.maven.plugins:maven-archetype-plugin:2.4:generate</code> command completes successfully and generates the expected result, the <code>mvn org.apache.maven.plugins:maven-archetype-plugin:generate</code> generates this error:</p>
  
  <pre><code>[WARNING] Error initializing: org.codehaus.plexus.velocity.DefaultVelocityComponent@4fbb001b
  java.lang.NoClassDefFoundError: org/apache/commons/lang/StringUtils
  ...
  Caused by: java.lang.ClassNotFoundException: org.apache.commons.lang.StringUtils
      at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass (SelfFirstStrategy.java:50)
      at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass (ClassRealm.java:271)
      at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:247)
      at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass (ClassRealm.java:239)
      at org.apache.velocity.runtime.resource.ResourceManagerImpl.initialize (ResourceManagerImpl.java:161)
  ...
  
  [ERROR] Failed to execute goal org.apache.maven.plugins:maven-archetype-plugin:3.1.0:generate (default-cli) on project standalone-pom: Execution default-cli of goal org.apache.maven.plugins:maven-archetype-plugin:3.1.0:generate failed: A required class was missing while executing org.apache.maven.plugins:maven-archetype-plugin:3.1.0:generate: org/apache/commons/lang/StringUtils
  </code></pre>
  
  <p>Is this a bug in the new version of maven-archetype-plugin or could this possibly due to some missing configuration on my side?</p>