The package from
<https://build.opensuse.org/package/show/security:privacy/gkeyring> requires a
package python-gnomekeyring which is not available for openSUSE_Leap_15.0 in
OBS. On openSUSE_Leap_42.3 the related package belongs to
gnome-python-desktop.src.rpm, but this one does not seem to be available for
15.0.

To satisfy the dependencies, could the missing package be added to the
distribution or some other repo in OBS, please?

FWIW, looking at the build status in OBS, it seems that a similar issue exists
for openSUSE_Tumbleweed, at least.

FWIW2: I branched the gnome-python-desktop from 42.3 in my home:mhnovell
repository and built it successfully for 15.0; gkeyring does work for me now.