Issue 1:
Bug report

pip install matplotlib fails today on kiwisolver error on Mac. Something broke on kiwisolver update that was pushed recently (https://pypi.org/project/kiwisolver/#history). Related issue - nucleic/kiwi#66

Code for reproduction

conda create -n kiwi-bug python-3.6
conda activate kiwi-bug . # or source activate kiwi-bug
pip install matplotlib

Actual outcome

Issue 2:
Since today, when I try to install matplotlib on macOS via pip, the installation fails while trying to build kiwisolver. Can we ensure that all dependencies of matplotlib provide wheels?

log

...
Building wheels for collected packages: kiwisolver
Building wheel for kiwisolver (setup.py) ... error
Complete output from command /Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/ll/rgszt4s525s2xtv8rr60lqz40000gn/T/pip-install-t9u3qteo/kiwisolver/setup.py';f=getattr(tokenize, 'o$
en', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /private/var/folders/ll/rgszt4s525s2xtv8rr60lqz40000gn/T/pip-wheel-gp3bw9o8 --python-tag cp36:
running bdist_wheel
running build
running build_ext
building 'kiwisolver' extension
creating build
creating build/temp.macosx-10.7-x86_64-3.6
creating build/temp.macosx-10.7-x86_64-3.6/py
gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/include -arch x86_64 -I/Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/include -ar$
h x86_64 -I. -I/Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/include/python3.6m -c py/kiwisolver.cpp -o build/temp.macosx-10.7-x86_64-3.6/py/kiwisolver.o
warning: include path for stdlibc++ headers not found; pass '-stdlib=libc++' on the command line to use the libc++ standard library instead [-Wstdlibcxx-not-found]
In file included from py/kiwisolver.cpp:9:
In file included from ./kiwi/kiwi.h:9:
./kiwi/constraint.h:9:10: fatal error: 'map' file not found
#include
^~~~~
1 warning and 1 error generated.
error: command 'gcc' failed with exit status 1

----------------------------------------
Failed building wheel for kiwisolver
Running setup.py clean for kiwisolver
Failed to build kiwisolver
Installing collected packages: mpmath, sympy, click, pyparsing, six, cycler, python-dateutil, kiwisolver, matplotlib, coverage, py, atomicwrites, attrs, pluggy, more-itertools, pytest, pytest-cov, sphinxcontrib-jsmath, docutils, MarkupSafe, jinja2, snowballstemmer, sphin$
contrib-htmlhelp, imagesize, chardet, urllib3, idna, requests, pytz, babel, sphinxcontrib-serializinghtml, sphinxcontrib-applehelp, packaging, sphinxcontrib-devhelp, alabaster, sphinxcontrib-qthelp, Pygments, sphinx, better-apidoc, sphinx-autodoc-typehints, isort, appdir$
, toml, black, decorator, ipython-genutils, traitlets, pyrsistent, jsonschema, jupyter-core, nbformat, webencodings, bleach, mistune, testpath, defusedxml, entrypoints, pandocfilters, nbconvert, tornado, ptyprocess, terminado, pyzmq, Send2Trash, jupyter-client, appnope, $
cwidth, prompt-toolkit, pickleshare, pexpect, parso, jedi, backcall, ipython, ipykernel, prometheus-client, notebook, jupyter-console, widgetsnbextension, ipywidgets, qtconsole, jupyter, argh, PyYAML, pathtools, watchdog, port-for, livereload, sphinx-autobuild, sphinx-rt$
-theme, smmap2, gitdb2, gitpython, apipkg, execnet, pytest-forked, pytest-xdist, watermark, virtualenv, nodeenv, zipp, importlib-metadata, identify, cfgv, importlib-resources, aspy.yaml, pre-commit, pep8, nbval, pycodestyle, pyflakes, mccabe, flake8, readme-renderer, req$
ests-toolbelt, pkginfo, tqdm, twine, nbsphinx, qdyn
Running setup.py install for kiwisolver ... error
Complete output from command /Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/ll/rgszt4s525s2xtv8rr60lqz40000gn/T/pip-install-t9u3qteo/kiwisolver/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/ll/rgszt4s525s2xtv8rr60lqz40000gn/T/pip-record-dv16j2ct/install-record.txt --single-version-externally-managed --compile:
running install
running build
running build_ext
building 'kiwisolver' extension
creating build
creating build/temp.macosx-10.7-x86_64-3.6
creating build/temp.macosx-10.7-x86_64-3.6/py
gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/include -arch x86_64 -I/Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/include -$
rch x86_64 -I. -I/Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/include/python3.6m -c py/kiwisolver.cpp -o build/temp.macosx-10.7-x86_64-3.6/py/kiwisolver.o
warning: include path for stdlibc++ headers not found; pass '-stdlib=libc++' on the command line to use the libc++ standard library instead [-Wstdlibcxx-not-found]
In file included from py/kiwisolver.cpp:9:
In file included from ./kiwi/kiwi.h:9:
./kiwi/constraint.h:9:10: fatal error: 'map' file not found
#include <map>
^~~~~
1 warning and 1 error generated.
error: command 'gcc' failed with exit status 1

----------------------------------------
Command "/Users/goerz/Documents/Programming/github/qdynpylib/.venv/py36/bin/python -u -c "import setuptools, tokenize;__file__='/private/var/folders/ll/rgszt4s525s2xtv8rr60lqz40000gn/T/pip-install-t9u3qteo/kiwisolver/setup.py';f=getattr(tokenize, 'open', open)(__file__);$
ode=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /private/var/folders/ll/rgszt4s525s2xtv8rr60lqz40000gn/T/pip-record-dv16j2ct/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in
/private/var/folders/ll/rgszt4s525s2xtv8rr60lqz40000gn/T/pip-install-t9u3qteo/kiwisolver/
make: *** [.venv/py36/bin/py.test] Error 1