This is because the package tries to overwrite another packages files without declaring a replaces relation. See policy 7.6 at
https://www.debian.org/doc/debian-policy/ch-relationships.html#overwriting-files-and-replacing-packages-replaces.
According to the thread started at 200908071233.02813.holger@layer-acht.org these bugs are to be filed with severity serious.
The commandline to find these logs is:
COMMAND='grep -E "trying to overwrite (.*) which is also in package"'
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