想要使用igraph与python（2.7），所以我不得不安装需要py2cairo和pixman的cairo。不得不使用Homebrew（很明显py2cairo安装有一些问题，请参阅here）
$ 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，但它没有用;无法找到任何建议，任何人都可以提供帮助吗？