Improve log message when nexus does not have permission to store a proxied artifact

Saw this during an evaluation, Nexus logs "failed content integrity validation" when it doesn't have permission to write to a proxy repo's local storage location.

This led us believe that this was a checksum error. A better log message could have saved quite a bit of time.

INFO | jvm 1 | 2009/08/13 09:57:40 | 2009-08-13 09:57:40 DEBUG - o.s.n.p.s.r.RemoteR~:apacheH~ - Invoking HTTP GET method against remote location http://people.apache.org/repo/m2-incubating-repository/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.n.p.r.Repository:maven2 - Item ApacheIncubating:/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar failed content integrity validation.
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.n.p.s.l.LocalRe~:file - /org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar --> /maven/repository/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.n.p.r.Repository:maven2 - deleteItem() :: ApacheIncubating:/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.n.p.s.l.LocalRe~:file - /org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar --> /maven/repository/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.n.p.r.Repository:maven2 - Item ApacheIncubating:/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar does not exist in local storage neither in remote storage, throwing ItemNotFoundException.
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.n.p.r.Repository:maven2 - ApacheIncubating retrieveItem() :: NOT FOUND ApacheIncubating:/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.n.p.r.Repository:maven2 - Adding path /org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar to NFC.
INFO | jvm 1 | 2009/08/13 09:57:50 | 2009-08-13 09:57:50 DEBUG - o.s.p.r.r.ManagedPl~:content - Got exception during processing GET http://ike.homebox.com:18081/nexus/content/repositories/ApacheIncubating/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar
INFO | jvm 1 | 2009/08/13 09:57:50 | org.sonatype.nexus.proxy.ItemNotFoundException: Item not found on UID ApacheIncubating:/org/apache/abdera/abdera-extensions-html/0.4.0-incubating/abdera-extensions-html-0.4.0-incubating.jar in repository ApacheIncubating
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.nexus.proxy.repository.AbstractProxyRepository.doRetrieveItem0(AbstractProxyRepository.java:619)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.nexus.proxy.repository.AbstractProxyRepository.doRetrieveItem(AbstractProxyRepository.java:430)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.nexus.proxy.maven.AbstractMavenRepository.doRetrieveItem(AbstractMavenRepository.java:331)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.nexus.proxy.repository.AbstractRepository.retrieveItem(AbstractRepository.java:796)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.nexus.proxy.repository.AbstractRepository.retrieveItem(AbstractRepository.java:603)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.nexus.proxy.router.DefaultRepositoryRouter.retrieveItem(DefaultRepositoryRouter.java:117)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.nexus.rest.AbstractResourceStoreContentPlexusResource.get(AbstractResourceStoreContentPlexusResource.java:122)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.sonatype.plexus.rest.resource.RestletResource.represent(RestletResource.java:260)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.restlet.resource.Resource.getRepresentation(Resource.java:303)
INFO | jvm 1 | 2009/08/13 09:57:50 | at org.restlet.resource.Resource.handleGet(Resource.java:465)