我之前找到的之前的答案都没有对我有用，但我最终还是在之前没有提到的另一个答案的帮助下解决了这个问题。这是实际的修复：
https://stackoverflow.com/a/20740964/2934226
CPPFLAGS 和 LDFLAGS 基本上不能在环境中设置；您需要将它们与配置命令一起设置，如下所示：
./configure CPPFLAGS="-I[openSSL install location]/include" LDFLAGS="-L[openSSL install location]/lib" [other flags here]
然后编译安装后就成功了！
$ python3 -c "import ssl; print(ssl.OPENSSL_VERSION)"
OpenSSL 1.0.2l 25 May 2017
以下是不起作用的地方，以及原因：
How do I compile Python 3.4 with custom OpenSSL? 没有帮助，因为您不能在环境中设置 LDFLAGS、CFLAGS 或 CPPFLAGS； setup.py 不会将它们传递给实际的编译步骤。即使设置 LD_LIBRARY_PATH 可能有效，您也不想这样做，因为它很危险（请参阅http://xahlee.info/UnixResource_dir/_/ldpath.html）。最后，--with-ssl 不是有效的配置参数，并且列出的用于添加它的补丁也不能完全应用。
Homebrew refusing to link OpenSSL 不适用于您尝试从源代码构建某些内容，而不是尝试获取已编译的 dylib 以查找重定位的库。此外，在 /usr/local 中创建符号链接是危险的，并且可能导致程序针对较新的标头进行编译，但使用较旧的系统二进制文件。
how to include ssl with python build on MacOS 无法正常工作。编辑 setup.py 以添加 lib 并包含安装我的 openSSL 部分 的目录，并允许您在 SSL 支持中进行编译。唉，它们无法导入，因为旧版本仍在使用中：
Following modules built successfully but were removed because they could not be imported:
_hashlib _ssl
[...]
building '_ssl' extension
gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -I/usr/local/opt/openssl/include/ -I./Include -I/oebuild/python/python-3.6.1/include -I. -I/usr/local/include -I/oebuild/python/src/Python-3.6.1/Include -I/oebuild/python/src/Python-3.6.1 -c /oebuild/python/src/Python-3.6.1/Modules/_ssl.c -o build/temp.macosx-10.11-x86_64-3.6/oebuild/python/src/Python-3.6.1/Modules/_ssl.o
gcc -bundle -undefined dynamic_lookup build/temp.macosx-10.11-x86_64-3.6/oebuild/python/src/Python-3.6.1/Modules/_ssl.o -L/oebuild/python/python-3.6.1/lib -L/usr/local/lib -lssl -lcrypto -o build/lib.macosx-10.11-x86_64-3.6/_ssl.cpython-36m-darwin.so
building '_hashlib' extension
gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -I/usr/local/opt/openssl/include/ -I./Include -I/oebuild/python/python-3.6.1/include -I. -I/usr/local/include -I/oebuild/python/src/Python-3.6.1/Include -I/oebuild/python/src/Python-3.6.1 -c /oebuild/python/src/Python-3.6.1/Modules/_hashopenssl.c -o build/temp.macosx-10.11-x86_64-3.6/oebuild/python/src/Python-3.6.1/Modules/_hashopenssl.o
gcc -bundle -undefined dynamic_lookup build/temp.macosx-10.11-x86_64-3.6/oebuild/python/src/Python-3.6.1/Modules/_hashopenssl.o -L/oebuild/python/python-3.6.1/lib -L/usr/local/lib -lssl -lcrypto -o build/lib.macosx-10.11-x86_64-3.6/_hashlib.cpython-36m-darwin.so
*** WARNING: renaming "_ssl" since importing it failed: dlopen(build/lib.macosx-10.11-x86_64-3.6/_ssl.cpython-36m-darwin.so, 2): Symbol not found: _CRYPTO_THREADID_set_callback
Referenced from: build/lib.macosx-10.11-x86_64-3.6/_ssl.cpython-36m-darwin.so
Expected in: flat namespace
in build/lib.macosx-10.11-x86_64-3.6/_ssl.cpython-36m-darwin.so
*** WARNING: renaming "_hashlib" since importing it failed: dlopen(build/lib.macosx-10.11-x86_64-3.6/_hashlib.cpython-36m-darwin.so, 2): Symbol not found: _HMAC_CTX_copy
Referenced from: build/lib.macosx-10.11-x86_64-3.6/_hashlib.cpython-36m-darwin.so
Expected in: flat namespace
in build/lib.macosx-10.11-x86_64-3.6/_hashlib.cpython-36m-darwin.so
otool -L 显示问题：
$ otool -L build/lib.macosx-10.11-x86_64-3.6/_ssl.cpython-36m-darwin_failed.so
build/lib.macosx-10.11-x86_64-3.6/_ssl.cpython-36m-darwin_failed.so:
/usr/lib/libssl.0.9.8.dylib (compatibility version 0.9.8, current version 0.9.8)
/usr/lib/libcrypto.0.9.8.dylib (compatibility version 0.9.8, current version 0.9.8)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1226.10.1)
（CRYPTO_THREADID是1.0.0版本引入的，据https://wiki.openssl.org/index.php/Manual:Threads(3)#HISTORY）