When is a <SQL> changeset considered to have failed?

Sql Server:

raiseError allows you to raise errors with varying severity. ( https://msdn.microsoft.com/en-us/library/ms178592.aspx )

a severity of >= 10 will jump you to a catch block, a severity >= 20 will kill the connection (although you require special permissions to throw severity >=19 errors).

my question is:

When will liquibase consider a custom sql script to have “failed” for abort/rollback/… purposes?

(liquibase doco at http://www.liquibase.org/documentation/changes/sql.html doesn’t specify anything to do with errors)