title: Missing link between Homebrew packages
body: <p>I have both <code>boost</code> and <code>boost-python</code> installed via <code>brew</code> on my MacOS 10.12 Sierra. However, <code>boost-python</code> doesn't seem to think that its dependency <code>boost</code> is installed:</p>
  
  <pre><code>$ brew info boost
  boost: stable 1.68.0 (bottled), HEAD
  Collection of portable C++ source libraries
  https://www.boost.org/
  /usr/local/Cellar/boost/1.65.1 (12,679 files, 401.2MB)
    Poured from bottle on 2017-10-28 at 09:19:27
  /usr/local/Cellar/boost/1.67.0_1 (13,506 files, 447.7MB) *
    Poured from bottle on 2018-05-18 at 03:58:16
  From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/boost.rb
  ==&gt; Dependencies
  Optional: icu4c ✔
  ==&gt; Options
  --with-icu4c
      Build regexp engine with icu support
  --without-single
      Disable building single-threading variant
  --without-static
      Disable building static library variant
  --HEAD
      Install HEAD version
  ==&gt; Caveats
  Building of Boost.Log is disabled because it requires newer GCC or Clang.
  ==&gt; Analytics
  install: 51,109 (30 days), 167,563 (90 days), 648,244 (365 days)
  install_on_request: 15,663 (30 days), 48,585 (90 days), 191,757 (365 days)
  build_error: 0 (30 days)
  
  $ brew info boost-python
  boost-python: stable 1.68.0 (bottled), HEAD
  C++ library for C++/Python2 interoperability
  https://www.boost.org/
  /usr/local/Cellar/boost-python/1.65.1 (457 files, 25MB)
    Built from source on 2017-10-28 at 09:23:57 with: --with-python3
  /usr/local/Cellar/boost-python/1.67.0 (459 files, 17.3MB) *
    Poured from bottle on 2018-05-18 at 03:58:20
  From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/boost-python.rb
  ==&gt; Dependencies
  Required: boost ✘
  ==&gt; Options
  --HEAD
      Install HEAD version
  ==&gt; Analytics
  install: 5,214 (30 days), 16,979 (90 days), 76,707 (365 days)
  install_on_request: 3,865 (30 days), 12,416 (90 days), 56,500 (365 days)
  build_error: 0 (30 days)
  </code></pre>
  
  <p>How do I get <code>boost-python</code> to recognize the existence of / link with  its dependency <code>boost</code>?</p>
  
  <p>It would be great if I could avoid uninstalling and reinstalling because there are so many other package dependencies on boost that took me a long/difficult time to get working.</p>
  
  <p>I'm doing this because: when compiling <a href="http://caffe.berkeleyvision.org/installation.html" rel="noreferrer">caffe</a>, it says <code>ld: library not found for -lboost_python</code>. Thank you.</p>