MacOS10.14，python安装Mysql-python出错，报ld: library not found for -lssl

解决方法：

1. 先确认是否安装mysql，如果没装，可以通过 brew install MySQL（有点慢），也可以下载dmg来安装
2. pip intall Mysql-python 出错，如果错误信息是 ld: library not found for -lssl，可以执行以下命令：

open /Library/Developer/CommandLineTools/Packages/macOS_SDK_headers_for_macOS_10.14.pkg

原因：

MacOS新版本，默认是没有Command Line Tools的，同时因为安全性原因 /usr/include 文件夹也没有，也不会给权限给我们编辑，可以通过 macOS_SDK_headers_for_macOS_10.14.pkg 帮我们安装一些 header头文件。

错误日志：

$ pip install MySQL-python
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7.
Collecting MySQL-python
..........
....省略很多日志
..........
                                        ~ ^~~~~~~~~~~
    _mysql.c:1506:11: warning: implicit conversion loses integer precision: 'unsigned long' to 'int' [-Wshorten-64-to-32]
                                    len = strlen(buf);
                                        ~ ^~~~~~~~~~~
    13 warnings generated.
    cc -bundle -undefined dynamic_lookup -Wl,-F. build/temp.macosx-10.14-intel-2.7/_mysql.o -L/usr/local/Cellar/[email protected]/5.7.26/lib -lmysqlclient -lssl -lcrypto -o build/lib.macosx-10.14-intel-2.7/_mysql.so
    ld: library not found for -lssl
    clang: error: linker command failed with exit code 1 (use -v to see invocation)
    error: command 'cc' failed with exit status 1
    ----------------------------------------
ERROR: Command "/usr/bin/python -u -c 'import setuptools, tokenize;__file__='"'"'/private/var/folders/zw/57wvjchn72n_gq259cjskt_c0000gn/T/pip-install-OOFRzg/MySQL-python/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/zw/57wvjchn72n_gq259cjskt_c0000gn/T/pip-record-NXkl0u/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/var/folders/zw/57wvjchn72n_gq259cjskt_c0000gn/T/pip-install-OOFRzg/MySQL-python/