Use the list of sources instead of an iterator in update-feeds looping task
This prevents RuntimeError due to dictionary size change that may occur (as a
result of a new source being added) during iteration.
Closes #3155843.
include *.py
include */*.py
recursive-include data *.gif *.png *.ico *.css *.js
recursive-include i18n *.po
recursive-include wdoc *