Comment 6 for bug 162196

This is source of problem (I suppose):
From cups 1.3.4 changelog:
"The scheduler did not reject requests with charsets other than US-ASCII or UTF-8, and the CUPS API incorrectly passed the locale charset to the scheduler instead of UTF-8"

evidence:
hp-toolbox fails if LC_ALL=pl_PL is set (Polish locale, usually ISO-8859-2 codepage, my default locale)

general fix, run from console to set LC_ALL to default English:
LC_ALL=C hp-toolbox

when I still use pl_PL for every localization variable and type:
LANG=C hp-toolbox
then hp-toolbox says there is no printer and red error appears on console:
"error: Invalid locale: C.utf8"

fix for Polish locale (Polish locale remains Polish but default ISO-8859-2 codepage is changed to UTF8:
LC_ALL=pl_PL.UTF8 hp-toolbox

Now the bad thing:
hp-testpage always fails:
LC_ALL=C hp-testpage
LC_ALL=pl_PL.UTF8 hp-testpage
so LC_ALL fix not works in this case at all.
However hp-testpage is not used very often so is not very important. However people may start reporting false bugs when they realize hp-testpage fails.

The problem may appear to all people using ISO-8859-* codepages selected by locale. It only exist since cups 1.3.4 so this error may appear more often when distro makers will begin to use cups 1.3.4

Here are my locale:
LANG=pl_PL
LC_CTYPE="pl_PL"
LC_NUMERIC="pl_PL"
LC_TIME="pl_PL"
LC_COLLATE="pl_PL"
LC_MONETARY="pl_PL"
LC_MESSAGES="pl_PL"
LC_PAPER="pl_PL"
LC_NAME="pl_PL"
LC_ADDRESS="pl_PL"
LC_TELEPHONE="pl_PL"
LC_MEASUREMENT="pl_PL"
LC_IDENTIFICATION="pl_PL"
LC_ALL=pl_PL