Default suffix returned by sanitizeRunSuffix when the input
contains no characters that survive the sanitiser. Chosen so a degenerate
input ("---", "@@@", whitespace) still produces a usable, non-empty
filename suffix instead of <date>-<type>--<lang>.html.
Default suffix returned by sanitizeRunSuffix when the input contains no characters that survive the sanitiser. Chosen so a degenerate input ("---", "@@@", whitespace) still produces a usable, non-empty filename suffix instead of
<date>-<type>--<lang>.html.