oauthlib===3.1.0 fails tests (requirements update)

[Matthew Thode]

  File "/home/zuul/src/opendev.org/openstack/keystone/.tox/py27/local/lib/python2.7/site-packages/oauthlib/oauth1/rfc5849/endpoints/access_token.py", line 106, in create_access_token_response
    request = self._create_request(uri, http_method, body, headers)
  File "/home/zuul/src/opendev.org/openstack/keystone/.tox/py27/local/lib/python2.7/site-packages/oauthlib/oauth1/rfc5849/endpoints/base.py", line 70, in _create_request
    headers = CaseInsensitiveDict(headers or {})
  File "/home/zuul/src/opendev.org/openstack/keystone/.tox/py27/local/lib/python2.7/site-packages/oauthlib/common.py", line 338, in __init__
    self.proxy = dict((k.lower(), k) for k in data)
  File "/home/zuul/src/opendev.org/openstack/keystone/.tox/py27/local/lib/python2.7/site-packages/oauthlib/common.py", line 338, in <genexpr>
    self.proxy = dict((k.lower(), k) for k in data)
AttributeError: 'tuple' object has no attribute 'lower'

https://review.opendev.org/675229 is a test review you can depend upon for testing fixes. Thanks

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/677511
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=48fad495405f6a97b7d85dd520e77e91ecc80e1e
Submitter: Zuul
Branch: master

commit 48fad495405f6a97b7d85dd520e77e91ecc80e1e
Author: Vishakha Agarwal <email address hidden>
Date: Tue Aug 20 22:08:08 2019 +0530

    Fix oauthlib update errors

    It seems flask is providing a class which is kind of
    hybrid between list & dict and provide this error
    because of this. Providing a dict instead of the
    werkzeug.datastructures.EnvironHeaders.

    Closes-Bug: #1839393
    Change-Id: Ic8e8e8153f4c812145ff3976c934c84f401f1019

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/keystone 16.0.0.0rc1 release candidate.