bad plugin configuration errors out

Added some formatting to the exception error message puked from the plexus container, and also in the project builder, where Xpp3 and IO exceptions are encountered...

this is another good candidate for ErrorDiagnoser. Such errors will come back as XPP3 errors, which means we can solve this problem by simply providing user-friendly feedback when the POM contains invalid XML.

not what I meant actually - the XML above is valid, but addClasspath is not recognised as it is not a mojo parameter on the jar plugin.

ah, yes. Maybe ErrorDiagnoser. Here is what I get, but would prefer a BUILD FAILURE:

[INFO] ----------------------------------------------------------------------------
[ERROR] BUILD ERROR
[INFO] ----------------------------------------------------------------------------
[ERROR] Cause:
org.apache.maven.plugin.MojoExecutionException: Error configuring plugin for execution of 'jar:jar'.
at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:430)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.processGoals(DefaultLifecycleExecutor.java:169)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:90)
at org.apache.maven.DefaultMaven.processProject(DefaultMaven.java:253)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:167)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:246)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:303)
at org.codehaus.classworlds.Launcher.launch(Launcher.java:243)
at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:416)
at org.codehaus.classworlds.Launcher.main(Launcher.java:363)
Caused by: org.apache.maven.plugin.PluginConfigurationException: Unable to parse the created DOM for plugin configuratio
n
at org.apache.maven.plugin.DefaultPluginManager.populatePluginFields(DefaultPluginManager.java:553)
at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:400)
... 13 more
Caused by: org.codehaus.plexus.component.configurator.ComponentConfigurationException: Class 'org.apache.maven.plugin.ja
r.JarMojo' does not contain a field named 'addClasspath'
at org.codehaus.plexus.component.configurator.converters.composite.ObjectWithFieldsConverter.getFieldByName(Obje
ctWithFieldsConverter.java:176)
at org.codehaus.plexus.component.configurator.converters.composite.ObjectWithFieldsConverter.processConfiguratio
n(ObjectWithFieldsConverter.java:112)
at org.codehaus.plexus.component.configurator.BasicComponentConfigurator.configureComponent(BasicComponentConfig
urator.java:54)
at org.apache.maven.plugin.DefaultPluginManager.populatePluginFields(DefaultPluginManager.java:548)
... 14 more

verified. This is ok, though I think we can still work on error reporting like this. There is still an open ticket for that.