For translations, do not report errors also present in English.
This resolves https://bugs.debian.org/983178 See the bug for more information.
Here is the effect on the number of error lines reported compared to the current situation, for each language:
~/tmp/www-master.debian.org/build-logs/validate$ mv en ..
~/tmp/www-master.debian.org/build-logs/validate$ for l in ??
> do printf "%-5s %3d %3d\n" $l "$(wc -l < $l)" "$(~/filter-validate-errors ../en $l|wc -l )"
> done
ar 13 0
bg 27 15
ca 14 2
cs 0 0
da 174 0
de 174 0
el 174 0
eo 0 0
es 174 0
fa 0 0
fi 0 0
fr 190 0
gl 0 0
he 0 0
hr 0 0
hu 13 0
hy 14 2
id 0 0
it 174 0
ja 0 0
ko 13 0
lt 0 0
nb 174 0
nl 174 0
pl 175 2
pt 174 0
ro 0 0
ru 174 0
sk 0 0
sv 175 2
ta 0 0
tr 0 0
uk 0 0
vi 0 0
zh-cn 174 0
zh-tw 174 0