Wrap time.sleep into wrapper function

In case if it was interrupted by SIGCHLD but scheduled awake time is not
reached it will continue sleeping. For all other signals behaviuor is
not changed.

tests/test_utils.py

@@ -0,0 +1,44 @@
+import os
+import time
+import unittest
+
+from helpers.utils import sigchld_handler, sigterm_handler, sleep
+
+
+def nop(*args, **kwargs):
+    pass
+
+
+def os_waitpid(a, b):
+    return (0, 0)
+
+
+def time_sleep(_):
+    sigchld_handler(None, None)
+
+
+class TestUtils(unittest.TestCase):
+
+    def __init__(self, method_name='runTest'):
+        self.setUp = self.set_up
+        self.tearDown = self.tear_down
+        super(TestUtils, self).__init__(method_name)
+
+    def set_up(self):
+        self.time_sleep = time.sleep
+        time.sleep = nop
+
+    def tear_down(self):
+        time.sleep = self.time_sleep
+
+    def test_sigterm_handler(self):
+        self.assertRaises(SystemExit, sigterm_handler, None, None)
+
+    def test_sigchld_handler(self):
+        sigchld_handler(None, None)
+        os.waitpid = os_waitpid
+        sigchld_handler(None, None)
+
+    def test_sleep(self):
+        time.sleep = time_sleep
+        sleep(0.01)