I get:

Making check in po
make[1]: Entering directory `/var/tmp/portage/www-client/epiphany-extensions-2.30.1/work/epiphany-extensions-2.30.1/po'
INTLTOOL_EXTRACT=/usr/bin/intltool-extract srcdir=. /usr/bin/intltool-update --gettext-package epiphany-extensions-2.29 --pot
rm -f missing notexist
srcdir=. /usr/bin/intltool-update -m
if [ -r missing -o -r notexist ]; then \
          exit 1; \
        fi
make[1]: Leaving directory `/var/tmp/portage/www-client/epiphany-extensions-2.30.1/work/epiphany-extensions-2.30.1/po'
Making check in help
make[1]: Entering directory `/var/tmp/portage/www-client/epiphany-extensions-2.30.1/work/epiphany-extensions-2.30.1/help'
xmllint --noout --noent --path C:./C --xinclude --postvalid ./C/epiphany-extensions.xml
xmllint --noout --noent --path es:./es --xinclude --postvalid ./es/epiphany-extensions.xml
./es/epiphany-extensions.xml:271: element para: validity error : Element placeholder-1 is not declared in para list of possible children
./es/epiphany-extensions.xml:271: element placeholder-1: validity error : No declaration for element placeholder-1
Document ./es/epiphany-extensions.xml does not validate
make[1]: *** [check-doc-docs] Error 3
make[1]: Leaving directory `/var/tmp/portage/www-client/epiphany-extensions-2.30.1/work/epiphany-extensions-2.30.1/help'
make: *** [check-recursive] Error 1

Thanks for solving it