Checkout SVN with credentials in Jenkins pipeline?
<p>How can I check out a Subversion repository that requires user credentials, via a Jenkins pipeline groovy script? It appears that the built-in <code>svn</code> command doesn't support credentials, so I tried code like this:</p>

<pre><code>node {
    stage 'checkout'
    withCredentials([[$class: 'UsernamePasswordMultiBinding',
                      credentialsId: '34761a89-1402-47d7-96e2-aec22ffdc50b',
                      usernameVariable: 'USERNAME', passwordVariable: 'PASSWORD']]) {
        sh "svn co https://trac.nci.org.au/svn/cable/branches/$SVN_BRANCH --username $USERNAME --password $PASSWORD cable_branch"
    }
}
</code></pre>

<p>But this fails with </p>

<pre><code>groovy.lang.MissingPropertyException: No such property: USERNAME for class: groovy.lang.Binding
    at groovy.lang.Binding.getVariable(Binding.java:63)
    at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onGetProperty(SandboxInterceptor.java:224)
    at org.kohsuke.groovy.sandbox.impl.Checker$4.call(Checker.java:241)
    at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:238)
    at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:221)
    at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:221)
    at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.getProperty(SandboxInvoker.java:23)
    at com.cloudbees.groovy.cps.impl.PropertyAccessBlock.rawGet(PropertyAccessBlock.java:17)
    at WorkflowScript.run(WorkflowScript:5)
    at ___cps.transform___(Native Method)
    ...
</code></pre>

<p>What am I missing?</p>