$ brew doctor
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: Unbrewed dylibs were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected dylibs:
    /usr/local/lib/libz.1.2.7.dylib
Warning: Unbrewed .pc files were found in /usr/local/lib/pkgconfig.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected .pc files:
    /usr/local/lib/pkgconfig/zlib.pc
Warning: Unbrewed static libraries were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected static libraries:
    /usr/local/lib/libz.a
Warning: /usr/bin occurs before /usr/local/bin
This means that system-provided programs will be used instead of those
provided by Homebrew. The following tools exist at both paths:

    2to3
    2to3-2.7
    idle
    idle2.5
    idle2.7
    pydoc
    pydoc2.5
    pydoc2.7
    python
    python-config
    python2.5
    python2.5-config
    python2.7
    python2.7-config
    pythonw
    pythonw2.5
    pythonw2.7
    scp
    sftp
    slogin
    smtpd.py
    smtpd2.5.py
    smtpd2.7.py
    sqlite3
    ssh
    ssh-add
    ssh-agent
    ssh-keygen
    ssh-keyscan

Consider amending your PATH so that /usr/local/bin
occurs before /usr/bin in your PATH.
Warning: Homebrew's sbin was not found in your path.
Consider amending your PATH variable so it contains:
  /usr/local/sbin