when opening a JarFile, report name of file in any errors

java.util.JarFile. can fail without reporting the name of the file it's
operating on. If you have a jarfile that isn't a valid zip, this can be
confusing.
Merge pull request #1584 from MichaelBlume/report-bad-filename

when opening a JarFile, report name of file in any errors
Merge remote-tracking branch 'upstream/master'