It is not possible to install marketplace-shibboleth-invitation on nuxeo-cap-6.0-HF24-SNAPSHOT-tomcat.
It works fine on 6.0 stock. Issue on 6.0-*SNAPSHOT comes from the dependency on nuxeo-6.0-HF18.
A released package can depend on a hotfix if it is not public. But a SNAPSHOT package cannot depend on a hotfix while it is not possible to install hotfix on SNAPSHOT distribution (similar to NXP-14085).