Adds function to return owner id of a process

Seems that is important have a default way to get a process owner id in
process utils module. This function will be useful soon when we have to
deal with timeout of sudo enabled processes.

Reference: https://trello.com/c/ROPWdFFrSigned-off-by: NCaio Carrara <ccarrara@redhat.com>

avocado/utils/process.py

@@ -1553,3 +1553,15 @@ def getstatusoutput(cmd, timeout=None, verbose=False, ignore_status=True,
     if text[-1:] == '\n':
         text = text[:-1]
     return (sts, text)
+
+
+def get_owner_id(pid):
+    """
+    Get the owner's user id of a process
+    param pid: process id
+    return: user id of the process owner
+    """
+    try:
+        return os.stat('/proc/%d/' % pid).st_uid
+    except OSError:
+        return None

selftests/unit/test_utils_process.py

@@ -296,6 +296,27 @@ class MiscProcessTests(unittest.TestCase):
         '''
         self.assertGreaterEqual(len(process.get_children_pids(1)), 1)
 
+    @mock.patch('avocado.utils.process.os.stat')
+    def test_process_get_owner_id(self, stat_mock):
+        process_id = 123
+        owner_user_id = 13
+        stat_mock.return_value = mock.Mock(st_uid=owner_user_id)
+
+        returned_owner_id = process.get_owner_id(process_id)
+
+        self.assertEqual(returned_owner_id, owner_user_id)
+        stat_mock.assert_called_with('/proc/%d/' % process_id)
+
+    @mock.patch('avocado.utils.process.os.stat')
+    def test_process_get_owner_id_with_pid_not_found(self, stat_mock):
+        process_id = 123
+        stat_mock.side_effect = OSError()
+
+        returned_owner_id = process.get_owner_id(process_id)
+
+        self.assertIsNone(returned_owner_id)
+        stat_mock.assert_called_with('/proc/%d/' % process_id)
+
 
 class CmdResultTests(unittest.TestCase):