想在 python (2.7) 中使用 igraph，所以我必须安装需要 py2cairo 和 pixman 的 cairo。必须使用 Homebrew（很明显 py2cairo 安装存在一些问题，请参见此处）
$ brew install py2cairo
Error: You must `brew link pixman cairo' before py2cairo can be installed
Linking /usr/local/Cellar/pixman/0.30.0... Warning: Could not link pixman. Unlinking...
Error: Could not symlink file: /usr/local/Cellar/pixman/0.30.0/include/pixman-1/pixman.h
Target /usr/local/include/pixman-1/pixman.h already exists. You may need to delete it.
To force the link and overwrite all other conflicting files, do:
brew link --overwrite formula_name
To list all files that would be deleted:
brew link --overwrite --dry-run formula_name
$ brew link --overwrite formula_name
Error: No such keg: /usr/local/Cellar/formula_name
我试图删除 pixman 文件，但没有用；找不到任何建议，有人可以帮忙吗？