Performs the same checks as the Rules Engine when issuing a commit, but without actually performing the commit.
Returns the string 'OK' if there are no violations. Otherwise, processing depends on the generate-error value.
NOTE: This method can NOT be called from a constraint.
The optional generate-error determines processing when there are violations. If it is not passed or if it is passed with the 'No' value, the relevant error message is returned. If it is passed with the 'Yes' value, any errors that occur are not returned, but processed as errors.