Runtime exception generated during a migration of repositories.
- advisory information on the (possibly null) subject of the import or export at the time the exception was
thrown. This is typically the
PullRequest being exported or
imported but may be any other type of object that is deemed appropriate. If the exception prevented the creation
of the subject itself so an instance is not available to pass in to this exception then the most relevant
containing entity or object is appropriate. If the subject was not known or the exception is not specifically
tied to any one subject (e.g. an IO exception while reading the export archive for import) then a null subject