Error handling for KPI Dashboard of API Manager if CanGetConsumers, CanGetAnyUser is not present

[karmaking]

To access the KPI Dashboard of the API Manager, the roles CanGetConsumers and CanGetAnyUser are required. Error handling does not work for this: If these roles are not given, "Internal Server Error (500)" is displayed and Gunicorn will throw an error in the logs.

[simonredfern]

Also need to check for all other Roles. e.g. CanReadAggregateMetrics

[simonredfern]

if don't have the role CanGetAnyUser then the Users page is just empty