As reported to ISC Support:

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Just to let you know we have run into a small hitch with packaging BIND 9.10.5 as it has added a python library which would currently be installed into site-packages/isc.

For our distribution we are seeking to have that installed into vendor-packages/isc.
In addition to changing the pathname we can see that we shall have to patch two python files that currently hard code 'site-packages'.

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> Looks like we can use distutils --install-lib=PATHNAME to our advantage.
> 

Patch file attached.