convert CVS to Mercurial : abort: decoding near

In my last post I wrote already about the conversion with the version from
the crew-repository and the builtin cvsps usage to convert a CVS
repository to a Mercurial repository:

hg convert --config convert.cvsps=builtin --datesort -A ~/hgUserNames ./gvs ./REPOS/GVS-hg
.....
275 Anpassungen im WFL Bereich für das Thema Abgeltungssteuer
transaction abort!
rollback completed
abort: decoding near 'hristoph K�rner ( ch': 'utf8' codec can't decode bytes in position 11-12: invalid data!
Now on a very large repository I got some aborts about out of memory and
problems in the native cvs executable, but the restart seems to continue.
But the last error as seen above was a conversion problem. Here in Austria
we have some Umlaute which caused problems.

Looking into the mercurial source I found the problem location in
mercurial/util.py in the function "fromlocal" where the UnicodeError is
logged.
The comment above also states the solution to solve the problem:

We attempt to decode strings using the encoding mode set by
HGENCODINGMODE, which defaults to 'strict'. In this mode, unknown
characters will cause an error message. Other modes include
'replace', which replaces unknown characters with a special
Unicode character, and 'ignore', which drops the character.
After I set HGENCODINGMODE the conversion finished.