Merge lp:~zulcss/charm-helpers/is_container into lp:charm-helpers

[Chuck Short]

Determine whether we are running inside a container or not.

=== modified file 'charmhelpers/core/host.py'
--- charmhelpers/core/host.py	2016-08-11 15:47:44 +0000
+++ charmhelpers/core/host.py	2016-10-24 13:03:43 +0000
@@ -732,3 +732,11 @@
                     assert unit == 'kB', 'Unknown unit'
                     return int(value) * 1024  # Classic, not KiB.
         raise NotImplementedError()
+
+def is_container():
+    """Return True if system is running inside a container"""
+    try:
+        return subprocess.check_output(
+            ['systemd-virt-check', '-c'])
+    except subprocess.CalledProcessError:
+        return False
 
=== modified file 'tests/core/test_host.py'
--- tests/core/test_host.py	2016-08-11 15:47:44 +0000
+++ tests/core/test_host.py	2016-10-24 13:03:43 +0000
@@ -1682,3 +1682,19 @@
             mock_file.readlines.return_value = raw.splitlines()
             self.assertEqual(host.get_total_ram(), 7266414592)  # 7GB
             mock_open.assert_called_once_with('/proc/meminfo', 'r')
+
+    @patch('subprocess.check_output')
+    def test_is_container_with_container(self, check_output):
+        check_output.return_value = 1
+        self.assertTrue(host.is_container())
+
+    @patch('subprocess.check_output')
+    def test_is_container_with_vm(self, check_output):
+        check_output.return_value = 0
+        self.assertFalse(host.is_container())
+    
+    @patch('subprocess.check_output')
+    def test_is_container_with_exception(self, check_output):
+        error = subprocess.CalledProcessError(1, 'oops', 'systemd-detect-virt')
+        check_output.side_effect = error
+        self.assertFalse(host.is_container())