v1.6.5

Bugfix release

• Proactively refresh credentials when applying and treat a missing
  access_token as invalid. Note: This change reveals surprising behavior
  between default credentials and batches. If you allow
  googleapiclient.discovery.build to use default credentials and specify
  different credentials by providing batch.execut() with an explicit http
  argument, your individual requests will use the default credentials and
  not the credentials specified to the batch http. To avoid this, tell
  build explicitly not to use default credentials by specifying
  build(..., http=httplib2.Http(). (#469)
• Remove mutual exclusivity check for developerKey and credentials (#465)
• Handle unknown media length. (#406)
• Handle variant error format gracefully. (#459)
• Avoid testing against Django >= 2.0.0 on Python 2. (#460)