Comment 0 for bug 1199197

https://github.com/openstack/trove/commit/4419cb1c035e430607492dbf066b463b8323d1d5#L2R125

The user's host is validated against the non_empty_string_pattern, which is defined as:

non_empty_string = {
    "type": "string",
    "minLength": 1,
    "maxLength": 255,
    "pattern": "^.*[0-9a-zA-Z]+.*$"
}

Previous to this commit, the --host flag was optional (it would conveniently default to '%'). This behavior has been broken, as well as the ability to include wildcards (via % and _).

Per http://dev.mysql.com/doc/refman/5.5/en/account-names.html, '%' and '_' are valid wildcard characters and host_ip/netmask is also an accepted format.

Note: If it was decided that defaulting the host was in poor taste, then the CLI should enforce the host argument (to be consistent) (see https://github.com/openstack/python-troveclient/blob/4ddb58ce9e609df3c0ac4be555f19643ef0511cc/troveclient/cli.py#L159)