swh/loader/core/loader.py has no proper test coverage

It's only tested via other modules.

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Migrated from T1393 (view on Phabricator)

mentioned in merge request !13 (closed)

mentioned in merge request !15 (closed)

added Core Loader priority:High labels

marked this issue as related to swh-environment#1411 (closed)

Resolved by !17 (closed).

assigned to @vlorentz

closed