Description of problem:

If you attempt to upload something that's not a zip file to candlepin, you'll get this error:

Jun 11 10:18:32 [http-8443-2] INFO  org.candlepin.sync.Importer - Extracting archive to: /var/cache/candlepin/sync/import5147580043996834060237220625044442
Jun 11 10:18:32 [http-8443-2] ERROR org.candlepin.sync.Importer - Exception caught importing archive
java.io.FileNotFoundException: /var/cache/candlepin/sync/import5147580043996834060237220625044442/consumer_export.zip (No such file or directory)
        at java.io.FileInputStream.open(Native Method)
        at java.io.FileInputStream.<init>(FileInputStream.java:137)
        at org.candlepin.sync.Importer.loadExport(Importer.java:181)
        at org.candlepin.resource.OwnerResource.importData(OwnerResource.java:888)

It would be better if candlepin verified that the uploaded file was in fact a zip file, and then printed an error if the file was not parsable for whatever reason. Throwing a FileNotFoundException can lead a sysadmin down the wrong path, checking file permissions and such.