Added explicit exception type for invalid artifact references

- Added an exception type to be thrown if the user specifies a
  syntactically incorrect reference to an artifact, e.g. as extra
  requirement. The new exception is a checked exception because in most
  cases it is caused by a configuration error. Having a checked
  exception encourages to add context information.
- Also: Fix typo in method name.

Bug: 352081
Change-Id: I4bb38f7070477f8e27d295e2afc0a816afadd6ef