Pin oauthlib to avoid breakage with 3.0.0 release.

We're going to release OAuthLib 3.0.0 soon, which contains some breaking changes.

This pinpoint is to avoid problems before we are able to address the compatibility.

Author: JonathanHuot

setup.cfg

@@ -28,7 +28,7 @@ include_package_data = True
 zip_safe = False
 install_requires =
 	django >= 2.0
-	oauthlib >= 2.0.3
+	oauthlib >= 2.0.3, < 3.0.0
 	requests >= 2.13.0
 
 [options.packages.find]