title: cx_Oracle pip install fails: oci.h: No such file or directory
body: <p>I'm a bit lost on this one. I also tried to install an older version of cx_Oracle, which I have installed in a separate virtualenv, but it also fails at the same place with the same error message.</p>
  
  <pre><code>$ pip install cx_Oracle
  (...)
  
  cx_Oracle.c:10:17: error: oci.h: No such file or directory
  cx_Oracle.c:11:18: error: orid.h: No such file or directory
  cx_Oracle.c:12:16: error: xa.h: No such file or directory
  
  error: command 'gcc' failed with exit status 1
  (...)
  ----------------------------------------
  Cleaning up...
  Command /R/.virtualenv/myenv/bin/python -c "import setuptools, tokenize;__file__='/R/.virtualenv/myenv/build/cx-Oracle/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-g5eyNG-record/install-record.txt --single-version-externally-managed --compile --install-headers /R/.virtualenv/myenv/include/site/python2.7 failed with error code 1 in /R/.virtualenv/myenv/build/cx-Oracle
  Traceback (most recent call last):
    File "/R/.virtualenv/myenv/bin/pip", line 11, in &lt;module&gt;
      sys.exit(main())
    File "/R/.virtualenv/myenv/lib/python2.7/site-packages/pip/__init__.py", line 185, in main
      return command.main(cmd_args)
    File "/R/.virtualenv/myenv/lib/python2.7/site-packages/pip/basecommand.py", line 161, in main
      text = '\n'.join(complete_log)
  UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 70: ordinal not in range(128)
  </code></pre>
  
  <p><a href="https://gist.github.com/dmvianna/e477f8de7996e04a8569" rel="noreferrer"><strong>full error log</strong></a></p>