Support python dict in sysctl_create

Add support for directly passing a python dict rather than a
YAML formatted string to sysctl_create to make it easier for
charms to set sane defaults without hopping via YAML first.

charmhelpers/core/sysctl.py

@@ -31,18 +31,22 @@
 def create(sysctl_dict, sysctl_file):
     """Creates a sysctl.conf file from a YAML associative array
 
-    :param sysctl_dict: a YAML-formatted string of sysctl options eg "{ 'kernel.max_pid': 1337 }"
+    :param sysctl_dict: a dict or YAML-formatted string of sysctl
+                        options eg "{ 'kernel.max_pid': 1337 }"
     :type sysctl_dict: str
     :param sysctl_file: path to the sysctl file to be saved
     :type sysctl_file: str or unicode
     :returns: None
     """
-    try:
-        sysctl_dict_parsed = yaml.safe_load(sysctl_dict)
-    except yaml.YAMLError:
-        log("Error parsing YAML sysctl_dict: {}".format(sysctl_dict),
-            level=ERROR)
-        return
+    if type(sysctl_dict) is not dict:
+        try:
+            sysctl_dict_parsed = yaml.safe_load(sysctl_dict)
+        except yaml.YAMLError:
+            log("Error parsing YAML sysctl_dict: {}".format(sysctl_dict),
+                level=ERROR)
+            return
+    else:
+        sysctl_dict_parsed = sysctl_dict
 
     with open(sysctl_file, "w") as fd:
         for key, value in sysctl_dict_parsed.items():

tests/core/test_sysctl.py

@@ -53,6 +53,25 @@ def test_create(self, mock_open):
             "sysctl", "-p",
             "/etc/sysctl.d/test-sysctl.conf"])
 
+    @patch(builtin_open)
+    def test_create_with_dict(self, mock_open):
+        """Test create sysctl method"""
+        _file = MagicMock(spec=io.FileIO)
+        mock_open.return_value = _file
+
+        create({"kernel.max_pid": 1337}, "/etc/sysctl.d/test-sysctl.conf")
+
+        _file.__enter__().write.assert_called_with("kernel.max_pid=1337\n")
+
+        self.log.assert_called_with(
+            "Updating sysctl_file: /etc/sysctl.d/test-sysctl.conf"
+            " values: {'kernel.max_pid': 1337}",
+            level='DEBUG')
+
+        self.check_call.assert_called_with([
+            "sysctl", "-p",
+            "/etc/sysctl.d/test-sysctl.conf"])
+
     @patch(builtin_open)
     def test_create_invalid_argument(self, mock_open):
         """Test create sysctl with an invalid argument"""