Comment # 58 on bug 927677 from Thomas Blume

(In reply to Pal Korossy from comment #56)
> Created attachment 777684 [details]
> Root password is reqested to mount in other session.

The password request comes from polkit-kde-authentication-agent-1:

-->
j�l 21 16:16:54 desktop polkitd[1039]: Registered Authentication Agent for
unix-session:8 (system bus name :1.1074
[/usr/lib64/libexec/polkit-kde-authentication-agent-1], object path
/org/kde/PolicyKit1/AuthenticationAgent, locale hu_HU.UTF-8)
j�l 21 16:16:54 desktop polkit-kde-authentication-agent-1[29180]:
Authentication agent result: true
j�l 21 16:18:23 desktop polkit-kde-authentication-agent-1[1954]: Listener
adapter polkit_qt_listener_initiate_authentication
j�l 21 16:18:23 desktop polkit-kde-authentication-agent-1[1954]:
GSimpleAsyncResult: 0x563ca8d4c900
j�l 21 16:18:23 desktop polkit-kde-authentication-agent-1[1954]:
polkit_qt_listener_initiate_authentication callback for  0x563ca8a1a6e0
j�l 21 16:18:23 desktop polkit-kde-authentication-agent-1[1954]: Initiating
authentication
j�l 21 16:18:23 desktop polkit-kde-authentication-agent-1[1954]: Message of
action:  "Hiteles�t�s sz�ks�ges a(z) General USB Flash Disk (/dev/sdd1)
csatol�s�hoz"
j�l 21 16:18:23 desktop polkit-kde-authentication-agent-1[1954]: Action
description has been found
j�l 21 16:19:21 desktop polkit-kde-authentication-agent-1[1954]: WinId of the
dialog is  35651603 35651603
j�l 21 16:19:21 desktop polkit-kde-authentication-agent-1[1954]: WinId of the
shown dialog is  35651603 35651603
j�l 21 16:19:21 desktop polkit-kde-authentication-agent-1[1954]: Trying again
j�l 21 16:19:21 desktop polkit-kde-authentication-agent-1[1954]: REQUEST
j�l 21 16:19:21 desktop polkit-kde-authentication-agent-1[1954]: Request: 
"Password: "
j�l 21 16:19:21 desktop polkit-kde-authentication-agent-1[1954]: "Password: "
--<

I cannot find official Leap15 packages for this agent at:

https://software.opensuse.org/package/polkit-kde-agent-1

Have you used the package from tumbleweed or a community package?
However, it would be better if you use an agent that is shipped with Leap15.