title: AttributeError: module 'pkg_resources' has no attribute 'safe_name' oauthlib install
body: <p>I'm trying to install tweepy (and by extension oauthlib), and I'm getting the following error when attempting to install:</p>
  
  <pre><code>Collecting requests-oauthlib&gt;=0.4.1 (from tweepy)
  Using cached requests_oauthlib-0.7.0-py2.py3-none-any.whl
  Collecting oauthlib&gt;=0.6.2 (from requests-oauthlib&gt;=0.4.1-&gt;tweepy)
    Using cached oauthlib-2.0.0.tar.gz
  Complete output from command python setup.py egg_info:
  Traceback (most recent call last):
    File "&lt;string&gt;", line 1, in &lt;module&gt;
    File "/private/var/folders/t7/751h0y1102z99ysr6659yjcr0000gn/T/pip-build-aoklhwtw/oauthlib/setup.py", line 70, in &lt;module&gt;
      'Topic :: Software Development :: Libraries :: Python Modules',
    File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/distutils/core.py", line 108, in setup
      _setup_distribution = dist = klass(attrs)
    File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/setuptools/dist.py", line 263, in __init__
      self.patch_missing_pkg_info(attrs)
    File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/setuptools/dist.py", line 246, in patch_missing_pkg_info
      key = pkg_resources.safe_name(str(attrs['name'])).lower()
  AttributeError: module 'pkg_resources' has no attribute 'safe_name'
  </code></pre>
  
  <p>Interestingly, the <code>/private/var/folders/t7/751h0y1102z99ysr6659yjcr0000gn/T/pip-build-aoklhwtw/oauthlib/</code> folder does not exist, so I can
  t even delete that/look at it closer.</p>
  
  <p>Any ideas what might cause this?</p>