问如何解决自制软件的权限？

我已经卸载并安装了3次Homebrew，因为它似乎永远不会允许我安装任何东西，因为它在大多数安装结束时拒绝我的权限。

作为一个例子，我将发布我目前面临的这个libjpeg下载场景。

我尝试安装libjpeg并得到：

$ brew install libjpeg

==> Downloading https://downloads.sf.net/project/machomebrew/Bottles/jpeg-8d.mountain_lion.bottle.1.tar.gz

Already downloaded: /Library/Caches/Homebrew/jpeg-8d.mountain_lion.bottle.1.tar.gz

==> Pouring jpeg-8d.mountain_lion.bottle.1.tar.gz

Warning: Could not link jpeg. Unlinking...

Error: The brew link step did not complete successfully

The formula built, but is not symlinked into /usr/local

You can try again using `brew link jpeg'

Error: Permission denied - /usr/local/opt/jpeg

“brew链接jpeg”结果

Error: Permission denied - /usr/local/opt/jpeg

如下问题：

$ brew docto

Warning: "config" scripts exist outside your system or Homebrew directories.

./configure scripts often look for *-config scripts to determine if

software packages are installed, and what additional flags to use when

compiling and linking.

Having additional scripts in your path can confuse software installed via

Homebrew if the config script overrides a system or Homebrew provided

script of the same name. We found the following "config" scripts:

/Library/Frameworks/Python.framework/Versions/2.7/bin/python-config

/Library/Frameworks/Python.framework/Versions/2.7/bin/python2-config

/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7-config

Warning: You have unlinked kegs in your Cella

Leaving kegs unlinked can lead to build-trouble and cause brews that depend on

those kegs to fail to run properly once built. Run brew link on these:

jpeg这个权限问题已经使任何事情都不可能使用brew，我真的很感激任何的建议。