The error is shown by doing this
>>> slicer.util.pip_install('psutil')
Collecting psutil
Using cached https://files.pythonhosted.org/packages/1c/ca/5b8c1fe032a458c2c4bcbe509d1401dca9dda35c7fc46b36bb81c2834740/psutil-5.6.3.tar.gz
Building wheels for collected packages: psutil
Building wheel for psutil (setup.py): started
Building wheel for psutil (setup.py): finished with status 'error'
Complete output from command /Applications/Slicer.app/Contents/bin/./python-real -u -c "import setuptools, tokenize;__file__='/private/var/folders/px/rkhksnnj0g91sxn5bvbrwzrc0000gn/T/pip-install-unz_qt1e/psutil/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /private/var/folders/px/rkhksnnj0g91sxn5bvbrwzrc0000gn/T/pip-wheel-go9_rzxt --python-tag cp36:
running bdist_wheel
running build
running build_py
creating build
creating build/lib.macosx-10.11-x86_64-3.6
creating build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_pswindows.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_common.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/__init__.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psosx.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psbsd.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psaix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_pslinux.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_compat.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psposix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_pssunos.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
creating build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_contracts.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_connections.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/runner.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_unicode.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_misc.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_posix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_linux.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_sunos.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/__init__.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_aix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_process.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_bsd.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_system.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_osx.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_memory_leaks.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_windows.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/__main__.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
running build_ext
building 'psutil._psutil_osx' extension
creating build/temp.macosx-10.11-x86_64-3.6
creating build/temp.macosx-10.11-x86_64-3.6/psutil
creating build/temp.macosx-10.11-x86_64-3.6/psutil/arch
creating build/temp.macosx-10.11-x86_64-3.6/psutil/arch/osx
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -pthread -Wall -g -fPIC -DPSUTIL_POSIX=1 -DPSUTIL_VERSION=563 -DPSUTIL_OSX=1 -I/Applications/Slicer.app/Contents/lib/Python/include/python3.6m -c psutil/_psutil_common.c -o build/temp.macosx-10.11-x86_64-3.6/psutil/_psutil_common.o
psutil/_psutil_common.c:9:10: fatal error: 'Python.h' file not found
#include <Python.h>
^~~~~~~~~~
1 error generated.
error: command '/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc' failed with exit status 1
----------------------------------------
Failed building wheel for psutil
Running setup.py clean for psutil
Failed to build psutil
Installing collected packages: psutil
Running setup.py install for psutil: started
Running setup.py install for psutil: finished with status 'error'
Complete output from command /Applications/Slicer.app/Contents/bin/./python-real -u -c "import setuptools, tokenize;__file__='/private/var/folders/px/rkhksnnj0g91sxn5bvbrwzrc0000gn/T/pip-install-unz_qt1e/psutil/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /private/var/folders/px/rkhksnnj0g91sxn5bvbrwzrc0000gn/T/pip-record-_4ag1w90/install-record.txt --single-version-externally-managed --compile:
running install
running build
running build_py
creating build
creating build/lib.macosx-10.11-x86_64-3.6
creating build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_pswindows.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_common.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/__init__.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psosx.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psbsd.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psaix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_pslinux.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_compat.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_psposix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
copying psutil/_pssunos.py -> build/lib.macosx-10.11-x86_64-3.6/psutil
creating build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_contracts.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_connections.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/runner.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_unicode.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_misc.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_posix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_linux.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_sunos.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/__init__.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_aix.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_process.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_bsd.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_system.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_osx.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_memory_leaks.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/test_windows.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
copying psutil/tests/__main__.py -> build/lib.macosx-10.11-x86_64-3.6/psutil/tests
running build_ext
building 'psutil._psutil_osx' extension
creating build/temp.macosx-10.11-x86_64-3.6
creating build/temp.macosx-10.11-x86_64-3.6/psutil
creating build/temp.macosx-10.11-x86_64-3.6/psutil/arch
creating build/temp.macosx-10.11-x86_64-3.6/psutil/arch/osx
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -pthread -Wall -g -fPIC -DPSUTIL_POSIX=1 -DPSUTIL_VERSION=563 -DPSUTIL_OSX=1 -I/Applications/Slicer.app/Contents/lib/Python/include/python3.6m -c psutil/_psutil_common.c -o build/temp.macosx-10.11-x86_64-3.6/psutil/_psutil_common.o
psutil/_psutil_common.c:9:10: fatal error: 'Python.h' file not found
#include <Python.h>
^~~~~~~~~~
1 error generated.
error: command '/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc' failed with exit status 1
----------------------------------------
Command "/Applications/Slicer.app/Contents/bin/./python-real -u -c "import setuptools, tokenize;__file__='/private/var/folders/px/rkhksnnj0g91sxn5bvbrwzrc0000gn/T/pip-install-unz_qt1e/psutil/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /private/var/folders/px/rkhksnnj0g91sxn5bvbrwzrc0000gn/T/pip-record-_4ag1w90/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/var/folders/px/rkhksnnj0g91sxn5bvbrwzrc0000gn/T/pip-install-unz_qt1e/psutil/
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "/Applications/Slicer.app/Contents/bin/Python/slicer/util.py", line 2057, in pip_install
logProcessOutput(proc)
File "/Applications/Slicer.app/Contents/bin/Python/slicer/util.py", line 2010, in logProcessOutput
raise CalledProcessError(retcode, proc.args, output=proc.stdout, stderr=proc.stderr)
subprocess.CalledProcessError: Command '['/Applications/Slicer.app/Contents/bin/../bin/PythonSlicer', '-m', 'pip', 'install', 'psutil']' returned non-zero exit status 1.
>>>
Somehow the SlicerPython has not the required devel headers in the python environment. This may result in more packages not being able to install.