Remove check for a failed googleapiclient upgrade (#522)

oauth2client is not even a required dependency now, so this check throws a confusing error message

Author: epall

apiclient/__init__.py

@@ -4,17 +4,6 @@
 
 import googleapiclient
 
-try:
-  import oauth2client
-except ImportError:
-  raise RuntimeError(
-      'Previous version of google-api-python-client detected; due to a '
-      'packaging issue, we cannot perform an in-place upgrade. To repair, '
-      'remove and reinstall this package, along with oauth2client and '
-      'uritemplate. One can do this with pip via\n'
-      '  pip install -I google-api-python-client'
-  )
-
 from googleapiclient import channel
 from googleapiclient import discovery
 from googleapiclient import errors