add AXFR source to OctoDNS

Adds a new source requested in #239. This source allows a user to pull data from
a legacy system (Bind9, etc.) that does not have an API/existing provider via
AXFR Zone Transfer.

tests/test_octodns_source_axfr.py

@@ -0,0 +1,40 @@
+#
+#
+#
+
+from __future__ import absolute_import, division, print_function, \
+    unicode_literals
+
+import dns.zone
+from dns.exception import DNSException
+
+from mock import patch
+from unittest import TestCase
+
+from octodns.source.axfr import AxfrSource, AxfrSourceZoneTransferFailed
+from octodns.zone import Zone
+
+
+class TestAxfrSource(TestCase):
+    source = AxfrSource('test', 'localhost')
+
+    forward_zonefile = dns.zone.from_file('./tests/zones/unit.tests.db',
+                                          'unit.tests', relativize=False)
+
+    @patch('dns.zone.from_xfr')
+    def test_populate(self, from_xfr_mock):
+        got = Zone('unit.tests.', [])
+
+        from_xfr_mock.side_effect = [
+            self.forward_zonefile,
+            DNSException
+        ]
+
+        self.source.populate(got)
+        self.assertEquals(11, len(got.records))
+
+        with self.assertRaises(AxfrSourceZoneTransferFailed) as ctx:
+            zone = Zone('unit.tests.', [])
+            self.source.populate(zone)
+        self.assertEquals('Unable to Perform Zone Transfer',
+                          ctx.exception.message)

tests/test_octodns_source_tinydns.py

@@ -15,7 +15,7 @@ from helpers import SimpleProvider
 
 
 class TestTinyDnsFileSource(TestCase):
-    source = TinyDnsFileSource('test', './tests/zones')
+    source = TinyDnsFileSource('test', './tests/zones/tinydns')
 
     def test_populate_normal(self):
         got = Zone('example.com.', [])

tests/zones/unit.tests.db

@@ -0,0 +1,42 @@
+$ORIGIN unit.tests.
+@           IN	SOA	ns1.unit.tests. root.unit.tests. (
+                        2018071501		; Serial
+                        3600    ; Refresh (1 hour)
+                        600     ; Retry (10 minutes)
+                        604800  ; Expire (1 week)
+                        3600    ; NXDOMAIN ttl (1 hour)
+                    )
+
+; NS Records
+@           3600  IN  NS  ns1.unit.tests.
+@           3600  IN  NS  ns2.unit.tests.
+under       3600  IN  NS  ns1.unit.tests.
+under       3600  IN  NS  ns2.unit.tests.
+
+; SRV Records
+_srv._tcp   600   IN  SRV 10 20 30 foo-1.unit.tests.
+_srv._tcp   600   IN  SRV 10 20 30 foo-2.unit.tests.
+
+; TXT Records
+txt         600   IN  TXT "Bah bah black sheep"
+txt         600   IN  TXT "have you any wool."
+txt         600   IN  TXT "v=DKIM1;k=rsa;s=email;h=sha256;p=A/kinda+of/long/string+with+numb3rs"
+
+; MX Records
+mx          300   IN  MX  10  smtp-4.unit.tests.
+mx          300   IN  MX  20  smtp-2.unit.tests.
+mx          300   IN  MX  30  smtp-3.unit.tests.
+mx          300   IN  MX  40  smtp-1.unit.tests.
+
+; A Records
+@           300   IN  A   1.2.3.4
+@           300   IN  A   1.2.3.5
+www         300   IN  A   2.2.3.6
+wwww.sub    300   IN  A   2.2.3.6
+
+; AAAA Records
+aaaa        600   IN  AAAA  2601:644:500:e210:62f8:1dff:feb8:947a
+
+; CNAME Records
+cname       300   IN  CNAME   unit.tests.
+included    300   IN  CNAME   unit.tests.