Trouble using maven-soapui-pro-plugin:4.0.0

I'm trying to use mavn-soapui-pro-plugin and I've added teh following dependencies for jgoodies.looks

<dependency>
<groupId>com.jgoodies</groupId>
<artifactId>looks</artifactId>
<version>2.2.0</version>
</dependency>

However, when I try to build it gives the following error:

Number of foreign imports: 1
import: Entry[import from realm ClassRealm[maven.api, parent: null]]

-----------------------------------------------------

at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:125)
... 20 more
Caused by: java.lang.NoClassDefFoundError: com/jgoodies/looks/plastic/theme/SkyBluer
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:631)
at java.lang.ClassLoader.defineClass(ClassLoader.java:615)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClassFromSelf(ClassRealm.java:386)
at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:42)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:244)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:230)
at com.eviware.soapui.SoapUIProTestCaseRunner.createSoapUICore(SourceFile:111)
at com.eviware.soapui.tools.AbstractSoapUIRunner.run(AbstractSoapUIRunner.java:143)
at com.eviware.soapui.maven2.TestMojo.execute(TestMojo.java:122)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
... 20 more
Caused by: java.lang.ClassNotFoundException: com.jgoodies.looks.plastic.theme.SkyBluer
at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:50)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:244)
at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:230)
... 37 more
[ERROR]


Any ideas why the error is thrown? your help is much appreciated.