Scan package pipelines fails to scan single file

[pombredanne]

A scan_package with https://repo1.maven.org/maven2/com/github/librepdf/openpdf-parent/1.3.11/openpdf-parent-1.3.11.pom will NOT scan the file at all, and results are empty.

[tdruez]

Code is ready at #1031 but blocked by aboutcode-org/purldb#263

[tdruez]

Implemented in #1031