Packages such as the following:

mgr-osa-dispatcher
python3-mgr-osa-common
python3-mgr-osa-dispatcher
python3-rhnlib
python3-suseRegisterInfo
suseRegisterInfo

Are being made available for openSUSE users via the SLE Updates repository
(http://download.opensuse.org/update/leap/15.3/sle/).

Such packages are part of the SUSE Manager Server/Proxy and must not be shipped
to openSUSE Leap (they are not even part of any SLE module.

There are more packages that should not be part of openSUSE Leap 15.3 either,
because they are part of the SUSE Manager Client tools, but again not part of
any SLE module. 

List of packages that must not be part can be checked at

SUSE:Channels/SLE-Manager-Tools_15_x86_64/_channel
SUSE:Channels/SLE-Module-SUSE-Manager-Proxy_4.2_x86_64/_channel
SUSE:Channels/SLE-Module-SUSE-Manager-Server_4.2_x86_64/_channel

Everything that matches the following regexes, should be excluded:

.+-?mgr-.+
.+-?rhnlib-.+
.+-?spacewalk-.+
.+-?suseRegisterInfo
.+-?zypp-plugin-spacewalk
.+-?uyuni-.+

I am not sure if that will exclude all the packages coming from SUSE Manager,
but should at least exclude those that are causing problems at the Uyuni
Server, as reported at Gitter:
https://gitter.im/uyuni-project/users?at=614d855863dca8189178e175