title: AttributeError: install_layout when attempting to install a package in a virtual environment
body: <p>I am trying to set up a virtual environment on my Ubuntu 15.10 PC. From my home directory, I have run the following commands:</p>
  
  <pre><code>virtualenv python
  source python/bin/activate
  pip install ujson
  </code></pre>
  
  <p>Below is the (bottom half of) content of <code>~/.pip/pip.log</code>:</p>
  
  <pre><code>running build                                                                    
  
  running build_ext                                                                
  
  building 'ujson' extension                                                       
  
  creating build                                                                   
  
  creating build/temp.linux-x86_64-2.7                                             
  
  creating build/temp.linux-x86_64-2.7/python                                      
  
  creating build/temp.linux-x86_64-2.7/lib                                         
  
  distcc clang-3.7 -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I./python -I./lib -I/usr/include/python2.7 -c ./python/ujson.c -o build/temp.linux-x86_64-2.7/./python/ujson.o -D_GNU_SOURCE
  
  distcc clang-3.7 -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I./python -I./lib -I/usr/include/python2.7 -c ./python/objToJSON.c -o build/temp.linux-x86_64-2.7/./python/objToJSON.o -D_GNU_SOURCE
  
  distcc clang-3.7 -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I./python -I./lib -I/usr/include/python2.7 -c ./python/JSONtoObj.c -o build/temp.linux-x86_64-2.7/./python/JSONtoObj.o -D_GNU_SOURCE
  
  distcc clang-3.7 -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I./python -I./lib -I/usr/include/python2.7 -c ./lib/ultrajsonenc.c -o build/temp.linux-x86_64-2.7/./lib/ultrajsonenc.o -D_GNU_SOURCE
  
  distcc clang-3.7 -fno-strict-aliasing -g -O2 -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I./python -I./lib -I/usr/include/python2.7 -c ./lib/ultrajsondec.c -o build/temp.linux-x86_64-2.7/./lib/ultrajsondec.o -D_GNU_SOURCE
  
  creating build/lib.linux-x86_64-2.7                                              
  
  gcc -pthread -shared build/temp.linux-x86_64-2.7/./python/ujson.o build/temp.linux-x86_64-2.7/./python/objToJSON.o build/temp.linux-x86_64-2.7/./python/JSONtoObj.o build/temp.linux-x86_64-2.7/./lib/ultrajsonenc.o build/temp.linux-x86_64-2.7/./lib/ultrajsondec.o -L/usr/lib -lpython2.7 -o build/lib.linux-x86_64-2.7/ujson.so
  
  running install_lib                                                              
  
  Traceback (most recent call last):                                               
  
    File "&lt;string&gt;", line 1, in &lt;module&gt;                                           
  
    File "/tmp/pip-build-v2tojT/ujson/setup.py", line 69, in &lt;module&gt;              
  
      classifiers=CLASSIFIERS,                                                     
  
    File "/usr/lib/python2.7/distutils/core.py", line 151, in setup                
  
      dist.run_commands()                                                          
  
    File "/usr/lib/python2.7/distutils/dist.py", line 953, in run_commands         
  
      self.run_command(cmd)                                                        
  
    File "/usr/lib/python2.7/distutils/dist.py", line 972, in run_command          
  
      cmd_obj.run()                                                                
  
    File "/home/quant/python/lib/python2.7/site-packages/setuptools/command/install.py", line 61, in run
  
      return orig.install.run(self)                                                
  
    File "/usr/lib/python2.7/distutils/command/install.py", line 575, in run       
  
      self.run_command(cmd_name)                                                   
  
    File "/usr/lib/python2.7/distutils/cmd.py", line 326, in run_command           
  
      self.distribution.run_command(command)                                       
  
    File "/usr/lib/python2.7/distutils/dist.py", line 971, in run_command          
  
      cmd_obj.ensure_finalized()                                                   
  
    File "/usr/lib/python2.7/distutils/cmd.py", line 109, in ensure_finalized      
  
      self.finalize_options()                                                      
  
    File "/home/quant/python/lib/python2.7/site-packages/setuptools/command/install_lib.py", line 17, in finalize_options
  
      self.set_undefined_options('install',('install_layout','install_layout'))    
  
    File "/usr/lib/python2.7/distutils/cmd.py", line 302, in set_undefined_options 
  
      getattr(src_cmd_obj, src_option))                                            
  
    File "/usr/lib/python2.7/distutils/cmd.py", line 105, in __getattr__           
  
      raise AttributeError, attr                                                   
  
  AttributeError: install_layout                                                   
  
  ----------------------------------------                                         
  Cleaning up...                                                                   
  Command /home/quant/python/bin/python2 -c "import setuptools, tokenize;__file__='/tmp/pip-build-v2tojT/ujson/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-rkdmJT-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/quant/python/include/site/python2.7 failed with error code 1 in /tmp/pip-build-v2tojT/ujson
  Exception information:                                                           
  Traceback (most recent call last):                                               
    File "/home/quant/python/lib/python2.7/site-packages/pip/basecommand.py", line 122, in main
      status = self.run(options, args)                                             
    File "/home/quant/python/lib/python2.7/site-packages/pip/commands/install.py", line 309, in run
      requirement_set.install(install_options, global_options, root=options.root_path)
    File "/home/quant/python/lib/python2.7/site-packages/pip/req.py", line 1436, in install
      requirement.install(install_options, global_options, *args, **kwargs)        
    File "/home/quant/python/lib/python2.7/site-packages/pip/req.py", line 707, in install
      cwd=self.source_dir, filter_stdout=self._filter_install, show_stdout=False)  
    File "/home/quant/python/lib/python2.7/site-packages/pip/util.py", line 716, in call_subprocess
      % (command_desc, proc.returncode, cwd))                                      
  InstallationError: Command /home/quant/python/bin/python2 -c "import setuptools, tokenize;__file__='/tmp/pip-build-v2tojT/ujson/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-rkdmJT-record/install-record.txt --single-version-externally-managed --compile --install-headers /home/quant/python/include/site/python2.7 failed with error code 1 in /tmp/pip-build-v2tojT/ujson
  </code></pre>
  
  <p>Some perhaps useful info:</p>
  
  <pre><code>(python)quant@OptiPlex-990:~$ pip --version
  pip 1.5.6 from /home/quant/python/lib/python2.7/site-packages (python 2.7)
  (python)quant@OptiPlex-990:~$ which python
  /home/quant/python/bin/python
  (python)quant@OptiPlex-990:~$ python --version
  Python 2.7.10
  </code></pre>
  
  <p>I have tried installing other packages (e.g. <code>numpy</code>) with similar outcomes; the compilation finishes, but it blows up when it tries to run <code>install_lib</code>.</p>