py: Fix line number printing for file with 1 line.
With a file with 1 line (and an error on that line), used to show the line as number 0. Now shows it correctly as line number 1. But, when line numbers are disabled, it now prints line number 1 for any line that has an error (instead of 0 as previously). This might end up being confusing, but requires extra RAM and/or hack logic to make it print something special in the case of no line numbers.