Login with umlauts in password does not work

[Masterwow3]

Describe the bug
Login with umlauts in password does not work.

To Reproduce
Steps to reproduce the behavior:

1. var c = new Client("https://domain.eu/", "user", "Vörker");
2. var list = c.List("/");
3. list is empty
4. After passwort change to Vorker it works

ownCloud / NextCloud version (required):
ownCloud 9