Below is cloud-init log entries around the warning.

Here are the contents of the lease file that dhclient wrote:
# cat /run/dhclient-lease-file 
lease {
  interface "ens3";
  fixed-address 54.36.113.86;
  option subnet-mask 255.255.255.255;
  option routers 54.36.112.1;
  option dhcp-lease-time 86400;
  option dhcp-message-type 5;
  option domain-name-servers 213.186.33.99;
  option dhcp-server-identifier 54.36.112.1;
  option interface-mtu 1500;
  option domain-name "openstacklocal";
  renew 5 2018/09/14 03:08:26;
  rebind 5 2018/09/14 13:45:08;
  expire 5 2018/09/14 16:45:08;
}




2018-09-13 16:45:08,843 - util.py[DEBUG]: Reading from /var/tmp/cloud-init/cloud-init-dhcp-seeuch_6/dhcp.leases (quiet=False)
2018-09-13 16:45:08,843 - util.py[DEBUG]: Read 442 bytes from /var/tmp/cloud-init/cloud-init-dhcp-seeuch_6/dhcp.leases
2018-09-13 16:45:08,844 - util.py[DEBUG]: Reading from /var/tmp/cloud-init/cloud-init-dhcp-seeuch_6/dhcp.leases (quiet=False)
2018-09-13 16:45:08,844 - util.py[DEBUG]: Read 442 bytes from /var/tmp/cloud-init/cloud-init-dhcp-seeuch_6/dhcp.leases
2018-09-13 16:45:08,844 - dhcp.py[DEBUG]: Received dhcp lease on ens3 for 54.36.113.86/255.255.255.255
2018-09-13 16:45:08,844 - __init__.py[DEBUG]: Attempting setup of ephemeral network on ens3 with 54.36.113.86/32 brd 54.36.113.86
2018-09-13 16:45:08,844 - util.py[DEBUG]: Running command ['ip', '-family', 'inet', 'addr', 'add', '54.36.113.86/32', 'broadcast', '54.36.113.86', 'dev', 'ens3'] with allowed return codes [0] (shell=False, capture=True)
2018-09-13 16:45:08,848 - util.py[DEBUG]: Running command ['ip', '-family', 'inet', 'link', 'set', 'dev', 'ens3', 'up'] with allowed return codes [0] (shell=False, capture=True)
2018-09-13 16:45:08,850 - util.py[DEBUG]: Running command ['ip', 'route', 'show', '0.0.0.0/0'] with allowed return codes [0] (shell=False, capture=True)
2018-09-13 16:45:08,853 - util.py[DEBUG]: Running command ['ip', '-4', 'route', 'add', 'default', 'via', '54.36.112.1', 'dev', 'ens3'] with allowed return codes [0] (shell=False, capture=True)
2018-09-13 16:45:08,856 - handlers.py[DEBUG]: finish: init-local/search-OpenStackLocal: FAIL: no local data found from DataSourceOpenStackLocal
2018-09-13 16:45:08,856 - util.py[WARNING]: Getting data from <class 'cloudinit.sources.DataSourceOpenStack.DataSourceOpenStackLocal'> failed
2018-09-13 16:45:08,856 - util.py[DEBUG]: Getting data from <class 'cloudinit.sources.DataSourceOpenStack.DataSourceOpenStackLocal'> failed
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/cloudinit/sources/__init__.py", line 601, in find_source
    if s.update_metadata([EventType.BOOT_NEW_INSTANCE]):
  File "/usr/lib/python3/dist-packages/cloudinit/sources/__init__.py", line 490, in update_metadata
    result = self.get_data()
  File "/usr/lib/python3/dist-packages/cloudinit/sources/__init__.py", line 182, in get_data
    return_value = self._get_data()
  File "/usr/lib/python3/dist-packages/cloudinit/sources/DataSourceOpenStack.py", line 131, in _get_data
    with EphemeralDHCPv4(self.fallback_interface):
  File "/usr/lib/python3/dist-packages/cloudinit/net/dhcp.py", line 63, in __enter__
    ephipv4.__enter__()
  File "/usr/lib/python3/dist-packages/cloudinit/net/__init__.py", line 648, in __enter__
    self._bringup_router()
  File "/usr/lib/python3/dist-packages/cloudinit/net/__init__.py", line 702, in _bringup_router
    'dev', self.interface], capture=True)
  File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 2067, in subp
    cmd=args)
cloudinit.util.ProcessExecutionError: Unexpected error while running command.
Command: ['ip', '-4', 'route', 'add', 'default', 'via', '54.36.112.1', 'dev', 'ens3']
Exit code: 2
Reason: -
Stdout:
Stderr: Error: Nexthop has invalid gateway.
2018-09-13 16:45:08,908 - main.py[DEBUG]: No local datasource found