Replace wait with communicate to avoid potential deadlock

Wait can deadlock when using stdout=PIPE and/or stderr=PIPE and the child
process generates enough output to a pipe such that it blocks waiting for
the OS pipe buffer to accept more data. Use communicate() to avoid that.

Change-Id: I452de95834a18a970ae78ab6c43d794151ce3300
closes-bug: 1372680

tempest/scenario/manager.py

@@ -624,7 +624,7 @@ class NeutronScenarioTest(ScenarioTest):
             proc = subprocess.Popen(cmd,
                                     stdout=subprocess.PIPE,
                                     stderr=subprocess.PIPE)
-            proc.wait()
+            proc.communicate()
             return (proc.returncode == 0) == should_succeed
 
         return tempest.test.call_until_true(
@@ -1832,7 +1832,7 @@ class NetworkScenarioTest(OfficialClientTest):
             proc = subprocess.Popen(cmd,
                                     stdout=subprocess.PIPE,
                                     stderr=subprocess.PIPE)
-            proc.wait()
+            proc.communicate()
             return (proc.returncode == 0) == should_succeed
 
         return tempest.test.call_until_true(
@@ -2267,7 +2267,7 @@ class OrchestrationScenarioTest(ScenarioTest):
             proc = subprocess.Popen(cmd,
                                     stdout=subprocess.PIPE,
                                     stderr=subprocess.PIPE)
-            proc.wait()
+            proc.communicate()
             return (proc.returncode == 0) == should_succeed
 
         return tempest.test.call_until_true(

tempest/stress/actions/ssh_floating.py

@@ -30,7 +30,7 @@ class FloatingStress(stressaction.StressAction):
         proc = subprocess.Popen(cmd,
                                 stdout=subprocess.PIPE,
                                 stderr=subprocess.PIPE)
-        proc.wait()
+        proc.communicate()
         success = proc.returncode == 0
         return success
 

tempest/tests/test_wrappers.py

@@ -62,14 +62,11 @@ class TestWrappers(base.TestCase):
         p = subprocess.Popen(
             "bash %s" % cmd, shell=True,
             stdout=subprocess.PIPE, stderr=subprocess.PIPE)
-        # wait in the general case is dangerous, however the amount of
-        # data coming back on those pipes is small enough it shouldn't be
-        # a problem.
-        p.wait()
+        out, err = p.communicate()
 
         self.assertEqual(
             p.returncode, expected,
-            "Stdout: %s; Stderr: %s" % (p.stdout.read(), p.stderr.read()))
+            "Stdout: %s; Stderr: %s" % (out, err))
 
     def test_pretty_tox(self):
         # Git init is required for the pbr testr command. pbr requires a git