Ignore paths when checking for empty Jekyll output

Author: ashawley

.travis.yml

@@ -19,5 +19,5 @@ script:
 - bundle exec jekyll build 2> error.log
 - cat >&2 error.log
 - ( ! grep -qie Error error.log )
-- find ./_site -empty ! -name error.log
-- find ./_site -empty ! -name error.log | ! read
+- find ./_site \( -type d \( -name events -o -name training \) -prune -false \) -o \( -type f ! -name error.log -empty \)
+- find ./_site \( -type d \( -name events -o -name training \) -prune -false \) -o \( -type f ! -name error.log -empty \) | ( ! read )