Error during deployment means cannot redeploy

While writing a test for JBAS-5912 I found a bug in Tomcat deployment.

Basically, it fails to deploy because the persistence context is "missing":

Caused by: java.lang.IllegalArgumentException: Can't find a persistence unit named 'test' in AbstractVFSDeploymentContext@29881315

{vfszip:/home/ejort/jboss-head/testsuite/output/lib/test-jpa-weblibs.war}

at org.jboss.jpa.resolvers.DefaultPersistenceUnitDependencyResolver.resolvePersistenceUnitSupplier(DefaultPersistenceUnitDependencyResolver.java:141)
at org.jboss.web.tomcat.service.TomcatInjectionContainer.resolvePersistenceUnitSupplier(TomcatInjectionContainer.java:652)
at org.jboss.injection.PersistenceUnitHandler.addPUDependency(PersistenceUnitHandler.java:124)
at org.jboss.injection.PersistenceContextHandler.loadXml(PersistenceContextHandler.java:76)
at org.jboss.web.tomcat.service.TomcatInjectionContainer.processMetadata(TomcatInjectionContainer.java:515)
at org.jboss.web.tomcat.service.WebCtxLoader.start(WebCtxLoader.java:158)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4251)
at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeployInternal(TomcatDeployment.java:354)

It then becomes impossible to fix because something is not undeployed properly.
Subsequent redeployments get the message:

org.jboss.deployers.spi.DeploymentException: Web mapping already exists for deployment URL file:/home/ejort/jboss-head/build/output/jboss-5.0.0.CR2/server/default/tmp/deploy/test-jpa-weblibs23565-exp.war/
at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeployInternal(TomcatDeployment.java:185)
at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeploy(TomcatDeployment.java:140)
at org.jboss.web.deployers.AbstractWarDeployment.start(AbstractWarDeployment.java:459)
at org.jboss.web.deployers.WebModule.startModule(WebModule.java:118)
at org.jboss.web.deployers.WebModule.start(WebModule.java:96)