title: exec-maven-plugin plugin error
body: <p>I use the exec-maven-plugin as follow</p>
  
  <pre><code>&lt;plugin&gt;
            &lt;artifactId&gt;exec-maven-plugin&lt;/artifactId&gt;
            &lt;groupId&gt;org.codehaus.mojo&lt;/groupId&gt;
            &lt;version&gt;1.6.0&lt;/version&gt;
            &lt;executions&gt;
              &lt;execution&gt;
                &lt;id&gt;npm install&lt;/id&gt;
                &lt;goals&gt;
                  &lt;goal&gt;exec&lt;/goal&gt;
                &lt;/goals&gt;
                &lt;phase&gt;generate-sources&lt;/phase&gt;
                &lt;configuration&gt;
                  &lt;executable&gt;${npm.executable}&lt;/executable&gt;
                  &lt;arguments&gt;
                    &lt;argument&gt;install&lt;/argument&gt;
                  &lt;/arguments&gt;
                  &lt;workingDirectory&gt;${basedir}/target/angular5/tourism&lt;/workingDirectory&gt;
                  &lt;target&gt;
                    &lt;echo message="Npm install" /&gt;
                  &lt;/target&gt;
                &lt;/configuration&gt;
              &lt;/execution&gt;
            &lt;/executions&gt;
          &lt;/plugin&gt;
  </code></pre>
  
  <p>I have the following error</p>
  
  <pre><code> java.io.IOException: Cannot run program "npm" (in directory "/Users/admin/Application-Marwen/workspace/Tourism/Tourism-Web/target/angular5/tourism"): error=2, No such file or directory
  </code></pre>
  
  <p>However the directory "/Users/admin/Application-Marwen/workspace/Tourism/Tourism-Web/target/angular5/tourism" exists and the command npm install works in this directory in the console. I have the Apache Maven 3.5.4 installed and use eclipse</p>