The SConstruct file at the top of the source tree in master and 2.2 branches uses tabs for indenting at lines 558, 560, 562 and 563.

The code works correctly because Python interprets each tab as 8 spaces, but it looks wrong in any editor set to show 4 spaces per tab. We should replace each tab with 8 spaces (which will make it look right) to prevent future accidents (and for consistency with the "don't use tabs" rule).