Comment 4 for bug 1491658

That error is know because of the systemd verbosity, not finding the module.
Indeed it has not yet been included into the upstream kernel source (many times explained on Phoronix or LKLM:
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KDBUS wasn't merged for Linux 4.3 even though there were previously expressed plans to do so.
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So that report is useless per se; except that systemd should only show warnings/errors about real included module(s) (which is not the case, as it also warns about PCC for example, only met with recent mobos)