Dump list of repos used if package not found

Print the list of repositories in use when unable to find a package. Extremely useful to avoid red herrings like when you mistyped a package name in an obscure way.
include Luis' suggestions
Merge pull request #136 from dzila/spma-dump-repos-when-fail

Dump list of repos used if package not found.

Useful for the migration from the 13.1 series.