$ brew doctor

Error: gettext was detected in your PREFIX.
The gettext provided by Homebrew is "keg-only", meaning it does not
get linked into your PREFIX by default.

If you `brew link gettext` then a large number of brews that don't
otherwise have a `depends_on 'gettext'` will pick up gettext anyway
during the `./configure` step.

If you have a non-Homebrew provided gettext, other problems will happen
especially if it wasn't compiled with the proper architectures.
Error: Some keg-only formula are linked into the Cellar.
Linking a keg-only formula, such as gettext, into the cellar with
`brew link f` will cause other formulae to detect them during the
`./configure` step. This may cause problems when compiling those
other formulae.

Binaries provided by keg-only formulae may override system binaries
with other strange results.

You may wish to `brew unlink` these brews:

    gettext
    pixman
Error: 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/libboost_filesystem-mt.dylib    /usr/local/lib/libboost_serialization-mt.dylib    /usr/local/lib/libboost_system-mt.dylib    /usr/local/lib/libencfs.6.dylib    /usr/local/lib/libmacfuse_i32.2.dylib    /usr/local/lib/libmacfuse_i64.2.dylib    /usr/local/lib/libosxfuse_i32.2.dylib    /usr/local/lib/libosxfuse_i64.2.dylib    /usr/local/lib/libprotobuf.6.dylib    /usr/local/lib/librlog.5.0.0.dylib    /usr/local/lib/libusb-0.1.4.4.4.dylib    /usr/local/lib/libusbpp-0.1.4.4.4.dylib
Error: Unbrewed .la files 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 .la files:
    /usr/local/lib/libosxfuse_i32.la    /usr/local/lib/libosxfuse_i64.la
Error: 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/osxfuse.pc
Error: You have unlinked kegs in your Cellar
Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
those kegs to fail to run properly once built.

    exiftool