##### SUMMARY

SyntaxWarning over using is for comparison of literals. The fix is simple and is a good beginner issue.

```
contrib/inventory/cobbler.py:218: SyntaxWarning: "is not" with a literal. Did you mean "!="?
  if this_dns_name is not None and this_dns_name is not "":
```

##### ISSUE TYPE

- Bug Report

##### COMPONENT NAME

cobbler

##### ANSIBLE VERSION

devel branch
""" Command line argument processing """
        parser = argparse.ArgumentParser(description='Produce an Ansible Inventory file based on Cobbler')
        parser.add_argument('--list', action='store_true', default=True, help='List instances (default: True)')
        parser.add_argument('--host', action='store', help='Get all the variables about a specific instance')
        parser.add_argument('--refresh-cache', action='store_true', default=False,
                            help='Force refresh of cache by making API requests to cobbler (default: False - use cache files)')
        self.args = parser.parse_args()
    def update_cache(self):
        """ Make calls to cobbler and save the output in a cache """
        self._connect()
        self.groups = dict()
        self.hosts = dict()
        if self.token is not None:
            data = self.conn.get_systems(self.token)
        else:
            data = self.conn.get_systems()
        for host in data:
            
            dns_name = host['hostname']  
            ksmeta = None
            interfaces = host['interfaces']