With python USE enabled, the build dies with the following error, building with USE="-python" completes and installs successfully, but is missing python functionality.

 * Package: sci-libs/xdmf2-1.0_p141226-r3
 * Repository: science-kit
 * Maintainer: sci@gentoo.org
 * USE: amd64 elibc_glibc kernel_linux python python_targets_python2_7 userland_GNU
 * FEATURES: preserve-libs sandbox userpriv usersandbox
>>> Unpacking source...
>>> Unpacking xdmf2-1.0_p141226.tar.xz to /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work
>>> Source unpacked in /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work
>>> Preparing source in /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226 ...
* Applying xdmf2-1.0_p141226-module.patch ...
 [ ok ]
* Applying xdmf2-1.0_p141226-cannot-find-hdf5-bug-591302.patch ...
 [ ok ]
* Applying xdmf2-1.0_p141226-cmake-3.12.patch ...
 [ ok ]
>>> Source prepared.
>>> Configuring source in /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226 ...
>>> Working in BUILD_DIR: "/var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226_build"
cmake -C /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226_build/gentoo_common_config.cmake -G Unix Makefiles -DCMAKE_INSTALL_PREFIX=/usr -DBUILD_SHARED_LIBS=1 -DXDMF_BUILD_DOCUMENTATION=no -DBUILD_TESTING=no -DXDMF_WRAP_PYTHON=yes -DCMAKE_BUILD_TYPE=Gentoo -DCMAKE_TOOLCHAIN_FILE=/var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226_build/gentoo_toolchain.cmake /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226
loading initial cache file /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226_build/gentoo_common_config.cmake
– The C compiler identification is GNU 7.3.1
– The CXX compiler identification is GNU 7.3.1
– Check for working C compiler: /usr/bin/x86_64-pc-linux-gnu-gcc
– Check for working C compiler: /usr/bin/x86_64-pc-linux-gnu-gcc – works
– Detecting C compiler ABI info
– Detecting C compiler ABI info - done
– Detecting C compile features
– Detecting C compile features - done
– Check for working CXX compiler: /usr/bin/x86_64-pc-linux-gnu-g++
– Check for working CXX compiler: /usr/bin/x86_64-pc-linux-gnu-g++ – works
– Detecting CXX compiler ABI info
– Detecting CXX compiler ABI info - done
– Detecting CXX compile features
– Detecting CXX compile features - done
– Found SWIG: /usr/bin/swig (found version "3.0.12")
– Found PythonInterp: /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/temp/python2.7/bin/python (found version "2.7.15")
– Found PythonLibs: /usr/lib/libpython2.7.so (found version "2.7.15")
– Found Git: /usr/bin/git (found version "2.19.1")
– Boost version: 1.65.0
– HDF5: Using hdf5 compiler wrapper to determine C configuration
– Found HDF5: /usr/lib64/libhdf5.so;/usr/lib64/libz.so;/usr/lib64/libdl.so;/usr/lib64/libm.so (found version "1.10.1")
– Found LibXml2: /usr/lib64/libxml2.so (found version "2.9.8")
– Check if the system is big endian
– Searching 16 bit integer
– Looking for sys/types.h
– Looking for sys/types.h - found
– Looking for stdint.h
– Looking for stdint.h - found
– Looking for stddef.h
– Looking for stddef.h - found
– Check size of unsigned short
– Check size of unsigned short - done
– Using unsigned short
– Check if the system is big endian - little endian
– Performing Test HAVE_BOOST_SHARED_DYNAMIC_CAST
– Performing Test HAVE_BOOST_SHARED_DYNAMIC_CAST - Failed
CMake Deprecation Warning at /usr/share/cmake/Modules/UseSWIG.cmake:492 (message):
SWIG_ADD_MODULE is deprecated. Use SWIG_ADD_LIBRARY instead.
Call Stack (most recent call first):
CMakeLists.txt:127 (swig_add_module)
core/CMakeLists.txt:147 (XDMF_SWIG_PYTHON)

CMake Deprecation Warning at /usr/share/cmake/Modules/UseSWIG.cmake:492 (message):
SWIG_ADD_MODULE is deprecated. Use SWIG_ADD_LIBRARY instead.
Call Stack (most recent call first):
CMakeLists.txt:127 (swig_add_module)
CMakeLists.txt:313 (XDMF_SWIG_PYTHON)

CMake Warning (dev) at CMake/XdmfFunctions.cmake:5 (if):
Policy CMP0054 is not set: Only interpret if() arguments as variables or
keywords when unquoted. Run "cmake --help-policy CMP0054" for policy
details. Use the cmake_policy command to set the policy and suppress this
warning.

Quoted variables like "lib" will no longer be dereferenced when the policy
is set to NEW. Since the policy is not set the OLD behavior will be used.
Call Stack (most recent call first):
CMakeLists.txt:352 (xdmf_create_config_file)
This warning is for project developers. Use -Wno-dev to suppress it.

– <<< Gentoo configuration >>>
Build type Gentoo
Install path /usr
Compiler flags:
C -march=westmere -O2 -pipe
C++ -march=westmere -O2 -pipe -std=c++14
Linker flags:
Executable Wl,-O1 -Wl,sort-common -Wl,-as-needed
Module Wl,-O1 -Wl,sort-common -Wl,-as-needed
Shared Wl,-O1 -Wl,sort-common -Wl,-as-needed

– Configuring done
CMake Error at CMakeLists.txt:135 (add_dependencies):
The dependency target "XdmfCore;XdmfDSM" of target "Xdmf" does not exist.
Call Stack (most recent call first):
CMakeLists.txt:313 (XDMF_SWIG_PYTHON)

– Generating done
– Build files have been written to: /var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226_build
* ERROR: sci-libs/xdmf2-1.0_p141226-r3::science-kit failed (configure phase):
* cmake failed
*
* Call stack:
* ebuild.sh, line 92: Called src_configure
* environment, line 3781: Called cmake-utils_src_configure
* environment, line 1020: Called die
* The specific snippet of code:
* "${CMAKE_BINARY}" "${cmakeargs[@]}" "${CMAKE_USE_DIR}" || die "cmake failed";
*
* If you need support, post the output of `emerge --info '=sci-libs/xdmf2-1.0_p141226-r3::science-kit'`,
* the complete build log and the output of `emerge -pqv '=sci-libs/xdmf2-1.0_p141226-r3::science-kit'`.
* The complete build log is located at '/var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/temp/build.log'.
* The ebuild environment file is located at '/var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/temp/environment'.
* Working directory: '/var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226_build'
* S: '/var/tmp/portage/sci-libs/xdmf2-1.0_p141226-r3/work/xdmf2-1.0_p141226'