title: install matplotlib using pip error(with raspberry pi 3b)
body: <p>I cant't install matplotlib. I'm using a raspberry pi 3b.</p>
  
  <p>I am using this </p>
  
  <pre><code>pip --no-cache-dir install matplotlib 
  </code></pre>
  
  <p>to install matplotlib. At the start it is all ok. But in <em>last</em> part,
  I get this error:</p>
  
  <pre><code>Exception:
  Traceback (most recent call last):
  File "/home/pi/.local/lib/python2.7/site-packages/pip/basecommand.py", 
  line 215, in main
  status = self.run(options, args)
  File "/home/pi/.local/lib/python2.7/site-
  packages/pip/commands/install.py", line 342, in run
  prefix=options.prefix_path,
  File "/home/pi/.local/lib/python2.7/site-packages/pip/req/req_set.py", 
  line 784, in install
  **kwargs
  File "/home/pi/.local/lib/python2.7/site-
  packages/pip/req/req_install.py", line 851, in install
  self.move_wheel_files(self.source_dir, root=root, prefix=prefix)
  File "/home/pi/.local/lib/python2.7/site-
  packages/pip/req/req_install.py", line 1064, in move_wheel_files
  isolated=self.isolated,
  File "/home/pi/.local/lib/python2.7/site-packages/pip/wheel.py", line 
  345, in move_wheel_files
  clobber(source, lib_dir, True)
  File "/home/pi/.local/lib/python2.7/site-packages/pip/wheel.py", line 
  316, in clobber
  ensure_dir(destdir)
  File "/home/pi/.local/lib/python2.7/site-packages/pip/utils/__init__.py", 
  line 83, in ensure_dir
  os.makedirs(path)
  File "/usr/lib/python2.7/os.py", line 157, in makedirs
  mkdir(name, mode)
  OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/dist-
  packages/backports.functools_lru_cache-1.5.dist-info'
  </code></pre>