In T2729#49743, @timeberhardt wrote:

That's my dirty hack (utf-8 hardcoded):

...

In T2729#48073, @timeberhardt wrote:

I can reproduce this bug with a fresh Kolab install on top of Ubuntu 16.04. I could not create new users after I added a user with an umlaut in his name.

The Bug is caused because in pykolab.utils the locale_name configured for the user (in my case de_DE) is fed to the python method locale.normalize which then returns de_DE.ISO8859-1. But the input string isn't latin but utf-8, so iconv can't convert the whole string and replaces the umlaut with a questionmark. As soon as I hardcoded utf-8 into the iconv call, everything was working again (of course that's not a solution).