add apt_key module

Pretty straightforward.  Give it a URL with an exported GPG key for signing an
Apt repository.  It downloads it and will install it using apt-key.  It's even
smart enough to tell if it's already there (i.e. actually tells you if it
changed or not).

test/TestRunner.py

@@ -10,6 +10,7 @@ import os
 import shutil
 import time
 import tempfile
+import urllib2
 
 from nose.plugins.skip import SkipTest
 
@@ -288,3 +289,64 @@ class TestRunner(unittest.TestCase):
         ])
         print result
         assert result['changed'] == False
+
+    def test_apt_key(self):
+        try:
+            key_file = self._get_test_file("apt_key.gpg")
+            key_file_url = 'file://' + urllib2.quote(key_file)
+            key_id = '473041FA'
+
+            os.environ['ANSIBLE_TEST_APT_KEY'] = 'none'
+            # key missing, should download and add
+            result = self._run('apt_key', ['state=present', 'url=' + key_file_url])
+            assert 'failed' not in result
+            assert result['added'] == 1
+            assert result['downloaded'] == 1
+            assert result['removed'] == 0
+            assert result['changed']
+
+            os.environ["ANSIBLE_TEST_APT_KEY"] = key_id
+            # key missing, shouldn't download, no changes
+            result = self._run('apt_key', ['id=12345678', 'state=absent', 'url=' + key_file_url])
+            assert 'failed' not in result
+            assert result['added'] == 0
+            assert result['downloaded'] == 0
+            assert result['removed'] == 0
+            assert not result['changed']
+            # key missing, should download and fail sanity check, no changes
+            result = self._run('apt_key', ['id=12345678', 'state=present', 'url=' + key_file_url])
+            assert 'failed' in result
+            assert result['added'] == 0
+            assert result['downloaded'] == 1
+            assert result['removed'] == 0
+            # key present, shouldn't download, no changes
+            result = self._run('apt_key', ['id=' + key_id, 'state=present', 'url=' + key_file_url])
+            assert 'failed' not in result
+            assert result['added'] == 0
+            assert result['downloaded'] == 0
+            assert result['removed'] == 0
+            assert not result['changed']
+            # key present, should download to get key id
+            result = self._run('apt_key', ['state=present', 'url=' + key_file_url])
+            assert 'failed' not in result
+            assert result['added'] == 0
+            assert result['downloaded'] == 1
+            assert result['removed'] == 0
+            assert not result['changed']
+            # key present, should download to get key id and remove
+            result = self._run('apt_key', ['state=absent', 'url=' + key_file_url])
+            assert 'failed' not in result
+            assert result['added'] == 0
+            assert result['downloaded'] == 1
+            assert result['removed'] == 1
+            assert result['changed']
+            # key present, should remove but not download
+            result = self._run('apt_key', ['id=' + key_id, 'state=absent', 'url=' + key_file_url])
+            assert 'failed' not in result
+            assert result['added'] == 0
+            assert result['downloaded'] == 0
+            assert result['removed'] == 1
+            assert result['changed']
+        finally:
+            # always clean up the environment
+            os.environ.pop('ANSIBLE_TEST_APT_KEY', None)