bug#9121: Error in ispell process

[Juri Linkov]

>> Do you even have a Russian dictionary installed?
>
> Probably not.  But the `coding-system-for-write' thing shows that the
> "Error in ispell" message may be coding-system-related.

It's not coding-system-related.  When you change the dictionary with e.g.
`M-x ispell-change-dictionary RET russian RET' then everything is ok.
This can be also confirmed with a standalone invocation:
`aspell -d russian --pipe'.

So the problem here is just with an uninformative and user-unfriendly
error message when the current dictionary mismatches the checked text.

But it's still better than when `ispell-region' just says:
"Spell-checking region using aspell with default dictionary...done"
like everything went fine.