Problem with error return from iconv (was: feature_request: log both args)

[sergey-safarov]

some program use this app to decoding emails.
in program log i see errors like {bad_charset,<<"UTF-8">>} generated by this module while called decode/1 function .
I looked to source and find that this error is generated from convert/1 and decode_body/4 while called iconv:open/2
I sure, From charset UTF-8 is correct.
I sure, wrong value in To charset. But this is not displayed in error message.
Could you add To value to error message

[sergey-safarov]

This happens because //IGNORE encodings is not supported by iconv on Alpine OS

bash-4.4# iconv -t "utf-8//IGNORE" -f "UTF-8" /tmp/aa.txt
iconv: destination charset utf-8//IGNORE: Invalid argument
bash-4.4# 
bash-4.4# cat /etc/os-release 
NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.7.0
PRETTY_NAME="Alpine Linux v3.7"
HOME_URL="http://alpinelinux.org"
BUG_REPORT_URL="http://bugs.alpinelinux.org"

[mworrell]

Isn't this a problem in iconv?