'Check simple quota limits.
For limits--those quotas for which there is no usage
synchronization function--this method checks that a set of
proposed values are permitted by the limit restriction.  The
values to check are given as keyword arguments, where the key
identifies the specific quota limit to check, and the value is
the proposed value.
This method will raise a QuotaResourceUnknown exception if a
given resource is unknown or if it is not a countable resource.
If any of the proposed values exceeds the respective quota defined
for the tenant, an OverQuota exception will be raised.
The exception will include a sorted list with the resources
which exceed the quota limit. Otherwise, the method returns nothing.
:param context: Request context
:param tenant_id: Tenant for which the quota limit is being checked
:param values: Dict specifying requested deltas for each resource'

def limit_check(self, context, tenant_id, **values):

    requested_resources = set(values.keys())
    managed_resources = set([res for res in resource_registry.get_all_resources() if (res in requested_resources)])
    unknown_resources = (requested_resources - managed_resources)
    if unknown_resources:
        raise exceptions.QuotaResourceUnknown(unknown=sorted(unknown_resources))
    return self.get_driver().limit_check(context, tenant_id, resource_registry.get_all_resources(), values)
