Allow license checking to continue if looking up a dependency fails

[kestred]

Looking up a dependency may fail for various reasons (the dependency might no longer exist at a git url, or alternatively it might be protected by access control or only available over a VPN that isn't connected, etc).

It would be nice to be able to see the license results for all dependencies which could be looked up successfully, perhaps by passing in a flag such as --skip-failures and emitting a warning like warning: Lookup a package's dependency failed, failed to find DEPENDENCY_NAME (DEPENDENCY_SOURCE) in 'DEPENDENT_PACKAGE'

[Nemo157]

Sounds like a good idea.