Uncaught Mercury exception:
Software Error: string.format: There is no first conversion specifier, but there is an input.
Stack dump follows:
   0       pred exception.throw/1-0 (erroneous) (exception.m:NNNN)
   1       pred require.error/1-0 (erroneous) (require.m:NNNN)
   2       pred string.format/3-0 (det) (string.m:NNNN)
   3       pred io.format/4-0 (det) (io.m:NNNN)
   4       pred string_format_test_2.main/2-0 (det) (string_format_test_2.m:13)