Inconsistent boost cmake file names

I'm not quite sure what is going on, and I'm not sure if this is a bug in mpi module or the cmake generation. Currently 1.71 build emits:

```
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi-1.71.0/libboost_mpi-variant-static.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi-1.71.0/boost_mpi-config-version.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi-1.71.0/boost_mpi-config.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi-1.71.0/libboost_mpi-variant-shared.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/mpi-1.71.0/mpi-config.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/mpi-1.71.0/mpi-config-version.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/mpi-1.71.0/libmpi-variant-shared-py3.8.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/mpi-1.71.0/libmpi-variant-shared-py3.7.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/mpi-1.71.0/libmpi-variant-static-py3.7.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/mpi-1.71.0/libmpi-variant-static-py3.8.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi_python-1.71.0/boost_mpi_python-config-version.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi_python-1.71.0/libboost_mpi_python-variant-static-py3.8.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi_python-1.71.0/libboost_mpi_python-variant-shared-py3.8.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi_python-1.71.0/libboost_mpi_python-variant-static-py3.7.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi_python-1.71.0/libboost_mpi_python-variant-shared-py3.7.cmake exists in debian/tmp but is not installed to anywhere
boost1.71_1.71.0-1_amd64.build:dh_missing: usr/lib/x86_64-linux-gnu/cmake/boost_mpi_python-1.71.0/boost_mpi_python-config.cmake exists in debian/tmp but is not installed to anywhere
```

And I can understand `boost_mpi-1.71.0/` and the `boost_mpi_python-1.71.0` but i am very confused about the `mpi-1.71.0/` as to what it is, and which library I should package it with: boost_mpi or boost_mpi_python or if it shouldn't exist at all!

Is it like cmake files generated for the compiled python mpi extension? ie. the one that is installed on Debian systems as:
```
-rw-r--r-- root/root 264 2019-03-12 03:44 ./usr/lib/python3/dist-packages/boost/__init__.py
-rw-r--r-- root/root 497112 2019-03-12 03:44 ./usr/lib/python3/dist-packages/boost/mpi.cpython-37m-x86_64-linux-gnu.so
-rw-r--r-- root/root 501208 2019-03-12 03:44 ./usr/lib/python3/dist-packages/boost/mpi.cpython-38-x86_64-linux-gnu.so
```

Frankly, I don't understand cmake files for boost here =)