Make > 3 name servers a warning, not a fatal error

This is useful when both IPv4 and IPv6 name servers are present.

https://bugs.launchpad.net/cloud-init/+bug/1670052
https://git.launchpad.net/cloud-init/commit/?id=657fd40f9ee692a817ec4614cd0d6cb0539ffabf

cloud-init-0.7.9-gt3-nameservers.patch

@@ -0,0 +1,44 @@
+Index: cloud-init-0.7.9/cloudinit/distros/parsers/resolv_conf.py
+===================================================================
+--- cloud-init-0.7.9.orig/cloudinit/distros/parsers/resolv_conf.py
++++ cloud-init-0.7.9/cloudinit/distros/parsers/resolv_conf.py
+@@ -6,9 +6,11 @@
+ 
+ from six import StringIO
+ 
++from cloudinit.distros.parsers import chop_comment
++from cloudinit import log as logging
+ from cloudinit import util
+ 
+-from cloudinit.distros.parsers import chop_comment
++LOG = logging.getLogger(__name__)
+ 
+ 
+ # See: man resolv.conf
+@@ -79,9 +81,10 @@ class ResolvConf(object):
+         if len(new_ns) == len(current_ns):
+             return current_ns
+         if len(current_ns) >= 3:
+-            # Hard restriction on only 3 name servers
+-            raise ValueError(("Adding %r would go beyond the "
+-                              "'3' maximum name servers") % (ns))
++            LOG.warn("ignoring nameserver %r: adding would "
++                     "exceed the maximum of "
++                     "'3' name servers (see resolv.conf(5))" % (ns))
++            return current_ns[:3]
+         self._remove_option('nameserver')
+         for n in new_ns:
+             self._contents.append(('option', ['nameserver', n, '']))
+Index: cloud-init-0.7.9/tests/unittests/test_distros/test_resolv.py
+===================================================================
+--- cloud-init-0.7.9.orig/tests/unittests/test_distros/test_resolv.py
++++ cloud-init-0.7.9/tests/unittests/test_distros/test_resolv.py
+@@ -46,7 +46,7 @@ class TestResolvHelper(TestCase):
+         self.assertNotIn('10.3', rp.nameservers)
+         self.assertEqual(len(rp.nameservers), 3)
+         rp.add_nameserver('10.2')
+-        self.assertRaises(ValueError, rp.add_nameserver, '10.3')
++        rp.add_nameserver('10.3')
+         self.assertNotIn('10.3', rp.nameservers)
+ 
+     def test_search_domains(self):

cloud-init.spec

@@ -55,6 +55,12 @@ Patch14:        cloud-init-0.7.9-systemd-cloud-final.patch
 # https://git.launchpad.net/cloud-init/commit/?id=f81d6c7bde2af206d449de593b35773068270c84
 Patch15:        cloud-init-0.7.9-sysconfig-iface.patch
 
+# Make > 3 name servers a warning, not a fatal error
+# This is useful when both IPv4 and IPv6 name servers are present.
+# https://bugs.launchpad.net/cloud-init/+bug/1670052
+# https://git.launchpad.net/cloud-init/commit/?id=657fd40f9ee692a817ec4614cd0d6cb0539ffabf
+Patch16:        cloud-init-0.7.9-gt3-nameservers.patch
+
 BuildArch:      noarch
 
 BuildRequires:  pkgconfig(systemd)
@@ -195,6 +201,7 @@ nosetests-%{python3_version} tests/unittests/ \
 - Fixed systemd dependency cycle with cloud-final and os-collect-config [RH:1420946, RH:1428492]
 - Fixed systemd dependency cycle with cloud-init and multi-user.target [RH:1428492, RH:1430511]
 - Fixed errors in network sysconfig handling [RH:1389530, LP:1665441]
+- Made > 3 name servers a warning, not a fatal error, unbreaking IPv6 setups [LP:1670052]
 
 * Fri Feb 10 2017 Fedora Release Engineering <releng@fedoraproject.org> - 0.7.9-3
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_26_Mass_Rebuild