Remove unnecessary check during setup (#518)

diff --git a/setup.py b/setup.py
index 07a4440..9ae3150 100644
--- a/setup.py
+++ b/setup.py
@@ -31,30 +31,6 @@
   sys.exit(1)
 
 from setuptools import setup
-import pkg_resources
-
-def _DetectBadness():
-  import os
-  if 'SKIP_GOOGLEAPICLIENT_COMPAT_CHECK' in os.environ:
-    return
-  o2c_pkg = None
-  try:
-    o2c_pkg = pkg_resources.get_distribution('oauth2client')
-  except pkg_resources.DistributionNotFound:
-    pass
-  oauth2client = None
-  try:
-    import oauth2client
-  except ImportError:
-    pass
-  if o2c_pkg is None and oauth2client is not None:
-    raise RuntimeError(
-        'Previous version of google-api-python-client detected; due to a '
-        'packaging issue, we cannot perform an in-place upgrade. Please remove '
-        'the old version and re-install this package.'
-    )
-
-_DetectBadness()
 
 packages = [
     'apiclient',