Define context.roles with base class

In f383bd2973c58c5272504603e4f9dddd55c5bb68, oslo.context (2.2.0)
added roles support in the context itself. This passes roles to
super()__init__.

requirements.txt updated to match global requirements. There is no
Proposal Bot request for this.

Change-Id: I1e00d8b2cf48403a7e2e4387431a835ecc69d86a

cloudkitty/common/context.py

@@ -37,13 +37,8 @@ class RequestContext(context.RequestContext):
                                              show_deleted=show_deleted,
                                              request_id=request_id,
                                              resource_uuid=resource_uuid,
-                                             overwrite=overwrite)
-        self.roles = roles or []
-
-    def to_dict(self):
-        d = super(RequestContext, self).to_dict()
-        d['roles'] = self.roles
-        return d
+                                             overwrite=overwrite,
+                                             roles=roles)
 
     @classmethod
     def from_dict(cls, values):

requirements.txt

@@ -13,7 +13,7 @@ PasteDeploy>=1.5.0 # MIT
 pecan>=1.0.0 # BSD
 WSME>=0.8 # MIT
 oslo.config>=3.7.0 # Apache-2.0
-oslo.context>=0.2.0 # Apache-2.0
+oslo.context>=2.2.0 # Apache-2.0
 oslo.concurrency>=3.5.0 # Apache-2.0
 oslo.db>=4.1.0 # Apache-2.0
 oslo.i18n>=2.1.0 # Apache-2.0