Update oauthlib to 2.0.3

[pyup-bot]

There's a new version of oauthlib available.
You are currently using 2.0.1. I have updated it to 2.0.3

These links might come in handy: PyPI | Changelog | Repo

Changelog

2.0.3

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• Address missing OIDC errors and fix a typo in the AccountSelectionRequired exception.
• Update proxy keys on CaseInsensitiveDict.update().
• Redirect errors according to OIDC's response_mode.
• Added universal wheel support.
• Added log statements to except clauses.
• According to RC7009 Section 2.1, a client should include authentication credentials when revoking its tokens.
  As discussed in 339, this is not make sense for public clients.
  However, in that case, the public client should still be checked that is infact a public client (authenticate_client_id).
• Improved prompt parameter validation.
• Added two error codes from RFC 6750.
• Hybrid response types are now be fragment-encoded.
• Added Python 3.6 to Travis CI testing and trove classifiers.
• Fixed BytesWarning issued when using a string placeholder for bytes object.
• Documented PyJWT dependency and improved logging and exception messages.
• Documentation improvements and fixes.

2.0.2

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• Dropped support for Python 2.6, 3.2 & 3.3.
• (FIX) OpenIDConnector will no longer raise an AttributeError when calling openid_authorization_validator() twice.

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖

[pyup-bot]

Closing this in favor of #167