Here is the error stacktrace I am getting when I try to install jsonnet. I am not sure what the error is caused by or if there is a way around it.

Collecting jsonnet
Downloading https://files.pythonhosted.org/packages/4a/f5/a0a41ac1f141a62c966291feff15e1829147462e95041bdc5fee1dcd7e0f/jsonnet-0.11.2.tar.gz (127kB)
100% |████████████████████████████████| 133kB 8.4MB/s
Building wheels for collected packages: jsonnet
Running setup.py bdist_wheel for jsonnet ... error
Complete output from command /usr/local/bin/python3.6 -u -c "import setuptools, tokenize;file='/private/var/folders/sp/4bfpfrfd4m3bx3nl84rvwd5w0000gn/T/pip-install-efhuihfi/jsonnet/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/sp/4bfpfrfd4m3bx3nl84rvwd5w0000gn/T/pip-wheel-tajcyg17 --python-tag cp36:
running bdist_wheel
running build
running build_ext
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/desugarer.cpp -o core/desugarer.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/formatter.cpp -o core/formatter.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/libjsonnet.cpp -o core/libjsonnet.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/lexer.cpp -o core/lexer.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/parser.cpp -o core/parser.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/pass.cpp -o core/pass.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/static_analysis.cpp -o core/static_analysis.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/string_utils.cpp -o core/string_utils.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 core/vm.cpp -o core/vm.o
c++ -c -g -O3 -Wall -Wextra -Woverloaded-virtual -pedantic -std=c++0x -fPIC -Iinclude -Ithird_party/md5 third_party/md5/md5.cpp -o third_party/md5/md5.o
building '_jsonnet' extension
creating build
creating build/temp.macosx-10.6-intel-3.6
creating build/temp.macosx-10.6-intel-3.6/python
/usr/bin/clang -fno-strict-aliasing -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -arch i386 -arch x86_64 -g -Iinclude -Ithird_party/md5 -I/Library/Frameworks/Python.framework/Versions/3.6/include/python3.6m -c python/_jsonnet.c -o build/temp.macosx-10.6-intel-3.6/python/_jsonnet.o
python/_jsonnet.c:147:19: warning: comparison of integers of different signs: 'int' and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]
for (i = 0; i < ctx->argc; ++i) {
~ ^ ~~~~~~~~~
1 warning generated.
python/_jsonnet.c:147:19: warning: comparison of integers of different signs: 'int' and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]
for (i = 0; i < ctx->argc; ++i) {
~ ^ ~~~~~~~~~
1 warning generated.
creating build/lib.macosx-10.6-intel-3.6
/usr/bin/clang++ -bundle -undefined dynamic_lookup -arch i386 -arch x86_64 -g build/temp.macosx-10.6-intel-3.6/python/_jsonnet.o core/desugarer.o core/formatter.o core/libjsonnet.o core/lexer.o core/parser.o core/pass.o core/static_analysis.o core/string_utils.o core/vm.o third_party/md5/md5.o -o build/lib.macosx-10.6-intel-3.6/_jsonnet.cpython-36m-darwin.so
clang: warning: libstdc++ is deprecated; move to libc++ with a minimum deployment target of OS X 10.9 [-Wdeprecated]
clang: warning: libstdc++ is deprecated; move to libc++ with a minimum deployment target of OS X 10.9 [-Wdeprecated]
ld: library not found for -lstdc++
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: command '/usr/bin/clang++' failed with exit status 1

Failed building wheel for jsonnet
Running setup.py clean for jsonnet
Failed to build jsonnet
Installing collected packages: jsonnet
Running setup.py install for jsonnet ... error
Complete output from command /usr/local/bin/python3.6 -u -c "import setuptools, tokenize;file='/private/var/folders/sp/4bfpfrfd4m3bx3nl84rvwd5w0000gn/T/pip-install-efhuihfi/jsonnet/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/sp/4bfpfrfd4m3bx3nl84rvwd5w0000gn/T/pip-record-f4v9_067/install-record.txt --single-version-externally-managed --compile:
running install
running build
running build_ext
make: core/desugarer.o' is up to date. make: core/formatter.o' is up to date.
make: core/libjsonnet.o' is up to date. make: core/lexer.o' is up to date.
make: core/parser.o' is up to date. make: core/pass.o' is up to date.
make: core/static_analysis.o' is up to date. make: core/string_utils.o' is up to date.
make: core/vm.o' is up to date. make: third_party/md5/md5.o' is up to date.
building '_jsonnet' extension
creating build
creating build/temp.macosx-10.6-intel-3.6
creating build/temp.macosx-10.6-intel-3.6/python
/usr/bin/clang -fno-strict-aliasing -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -arch i386 -arch x86_64 -g -Iinclude -Ithird_party/md5 -I/Library/Frameworks/Python.framework/Versions/3.6/include/python3.6m -c python/_jsonnet.c -o build/temp.macosx-10.6-intel-3.6/python/_jsonnet.o
python/_jsonnet.c:147:19: warning: comparison of integers of different signs: 'int' and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]
for (i = 0; i < ctx->argc; ++i) {
~ ^ ~~~~~~~~~
1 warning generated.
python/_jsonnet.c:147:19: warning: comparison of integers of different signs: 'int' and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]
for (i = 0; i < ctx->argc; ++i) {
~ ^ ~~~~~~~~~
1 warning generated.
creating build/lib.macosx-10.6-intel-3.6
/usr/bin/clang++ -bundle -undefined dynamic_lookup -arch i386 -arch x86_64 -g build/temp.macosx-10.6-intel-3.6/python/_jsonnet.o core/desugarer.o core/formatter.o core/libjsonnet.o core/lexer.o core/parser.o core/pass.o core/static_analysis.o core/string_utils.o core/vm.o third_party/md5/md5.o -o build/lib.macosx-10.6-intel-3.6/_jsonnet.cpython-36m-darwin.so
clang: warning: libstdc++ is deprecated; move to libc++ with a minimum deployment target of OS X 10.9 [-Wdeprecated]
clang: warning: libstdc++ is deprecated; move to libc++ with a minimum deployment target of OS X 10.9 [-Wdeprecated]
ld: library not found for -lstdc++
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: command '/usr/bin/clang++' failed with exit status 1

----------------------------------------

Command "/usr/local/bin/python3.6 -u -c "import setuptools, tokenize;file='/private/var/folders/sp/4bfpfrfd4m3bx3nl84rvwd5w0000gn/T/pip-install-efhuihfi/jsonnet/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/sp/4bfpfrfd4m3bx3nl84rvwd5w0000gn/T/pip-record-f4v9_067/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/var/folders/sp/4bfpfrfd4m3bx3nl84rvwd5w0000gn/T/pip-install-efhuihfi/jsonnet/