When prereqs cannot be determined, indexing stops and the current sandbox is not removed

[fgabolde]

{UNKNOWN}: Impossible to determine prereqs! at lib/ThisPAN/Indexing.pm line 264. at lib/ThisPAN/Indexing.pm line 270

In the indexer logs:

[Fri Jul 15 13:38:58 2016] Fetching URL [redacted]/authors/id/S/SH/SHERWOOD/xisofs-1.3.tar.gz
[Fri Jul 15 13:38:58 2016] File has been fetched via HTTP to /tmp/holR1zYx0S/xisofs-1.3.tar.gz
[Fri Jul 15 13:38:58 2016] Extracting distribution tarball /tmp/holR1zYx0S/xisofs-1.3.tar.gz to /tmp/holR1zYx0S
[Fri Jul 15 13:38:59 2016] Tarball has a single directory in it, good.
[Fri Jul 15 13:38:59 2016] Looking for metadata files...
[Fri Jul 15 13:38:59 2016] No usable META.json file.
[Fri Jul 15 13:38:59 2016] No usable META.yml file.
[Fri Jul 15 13:38:59 2016] No usable Build.PL file.
[logs end here]