Failing to validate GPL licenses

`licensing.validate()` has `'Unknown license key(s)'` error for GPL licenses, e.g. `'LGPLv2.1'`, `'GPLv2'`, `'GPL2'`.

Side note: Also some images have several licenses, e.g. `MIT`, `GPL2` and others.
When they are listed as `'MIT GPL2'` for example, it's okay, validation just fails with errors ('Unknown license key(s)').
But when they are listed with commas instead - `'MIT,GPL2'` it throws an exception for invalid characters.
In some cases, f.e. `photon:3.0` the licenses come in this form.
The latter can be easily resolved, but I just wonder if it would be better those use-cases to be
handled within the validate method instead?