code: def validate_quota_change(self, quota_deltas, raise_exception=False):
          
          errors = []
          for name, delta in six.iteritems(quota_deltas):
              quota = self.quotas.get(name=name)
              if quota.is_exceeded(delta):
                  errors.append('%s quota limit: %s, requires %s (%s)\n' % (
                      quota.name, quota.limit, quota.usage + delta, quota.scope))
          if not raise_exception:
              return errors
          else:
              if errors:
                  raise exceptions.QuotaExceededException(_('One or more quotas were exceeded: %s') % ';'.join(errors))
docs: Get error messages about object and his ancestor quotas that will be exceeded if quota_delta will be added.
  
          raise_exception - if True QuotaExceededException will be raised if validation fails
          quota_deltas - dictionary of quotas deltas, example:
          {
              'ram': 1024,
              'storage': 2048,
              ...
          }
          Example of output:
              ['ram quota limit: 1024, requires: 2048(instance#1)', ...]