title: pip install pygraphviz: No package 'libcgraph' found
body: <p>I succeed in installing <code>graphviz</code> and <code>cgraph</code> with</p>
  
  <pre><code>$ sudo pip install graphviz
  ....
  Successfully installed graphviz-0.5.1
  
  $ sudo pip install cgraph
  ...
  Successfully installed cgraph-0.1
  </code></pre>
  
  <p>I encounter the issue <code>No package 'libcgraph' found</code> while running <code>sudo pip install pygraphviz</code>. Below is the full stacktrace.</p>
  
  <pre><code>$ sudo pip install pygraphviz
  The directory '/Users/sparkandshine/Library/Caches/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
  The directory '/Users/sparkandshine/Library/Caches/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
  Collecting pygraphviz
    Downloading pygraphviz-1.3.1.zip (123kB)
      100% |████████████████████████████████| 133kB 1.5MB/s 
  Installing collected packages: pygraphviz
    Running setup.py install for pygraphviz ... error
      Complete output from command /usr/bin/python -u -c "import setuptools, tokenize;__file__='/private/tmp/pip-build-qfFpFG/pygraphviz/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-JmwjA6-record/install-record.txt --single-version-externally-managed --compile:
      running install
      Trying pkg-config
      Package libcgraph was not found in the pkg-config search path.
      Perhaps you should add the directory containing `libcgraph.pc'
      to the PKG_CONFIG_PATH environment variable
      No package 'libcgraph' found
      Traceback (most recent call last):
        File "&lt;string&gt;", line 1, in &lt;module&gt;
        File "/private/tmp/pip-build-qfFpFG/pygraphviz/setup.py", line 87, in &lt;module&gt;
          tests_require=['nose&gt;=0.10.1', 'doctest-ignore-unicode&gt;=0.1.0',],
        File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/core.py", line 151, in setup
          dist.run_commands()
        File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/dist.py", line 953, in run_commands
          self.run_command(cmd)
        File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/distutils/dist.py", line 972, in run_command
          cmd_obj.run()
        File "setup_commands.py", line 44, in modified_run
          self.include_path, self.library_path = get_graphviz_dirs()
        File "setup_extra.py", line 121, in get_graphviz_dirs
          include_dirs, library_dirs = _pkg_config()
        File "setup_extra.py", line 44, in _pkg_config
          output = S.check_output(['pkg-config', '--libs-only-L', 'libcgraph'])
        File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 573, in check_output
          raise CalledProcessError(retcode, cmd, output=output)
      subprocess.CalledProcessError: Command '['pkg-config', '--libs-only-L', 'libcgraph']' returned non-zero exit status 1
  
      ----------------------------------------
  Command "/usr/bin/python -u -c "import setuptools, tokenize;__file__='/private/tmp/pip-build-qfFpFG/pygraphviz/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" install --record /tmp/pip-JmwjA6-record/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/tmp/pip-build-qfFpFG/pygraphviz/
  </code></pre>
  
  <p>I tried the solutions provided by <a href="https://stackoverflow.com/questions/15661384/python-does-not-see-pygraphviz">Python does not see pygraphviz</a>, but it doesn't work. </p>