Storing off last 10 cout and cerr results from calling checkOutput to…

… report on failure. GH EOSIO#5199

tests/TestHelper.py

@@ -122,6 +122,12 @@ def shutdown(cluster, walletMgr, testSuccessful=True, killEosInstances=True, kil
             if walletMgr:
                 walletMgr.dumpErrorDetails()
             Utils.Print("== Errors see above ==")
+            if len(Utils.CheckOutputDeque)>0:
+                Utils.Print("== cout/cerr pairs from last %d calls to Utils. ==" % len(Utils.CheckOutputDeque))
+                for out, err in Utils.CheckOutputDeque:
+                    Utils.Print("cout={%s}" % (out))
+                    Utils.Print("cerr={%s}\n" % (out))
+                Utils.Print("== cout/cerr pairs done. ==")
 
         if killEosInstances:
             Utils.Print("Shut down the cluster.")

tests/testUtils.py

@@ -1,6 +1,7 @@
 import subprocess
 import time
 import os
+from collections import deque
 from collections import namedtuple
 import inspect
 import json
@@ -24,6 +25,7 @@ class Utils:
     EosLauncherPath="programs/eosio-launcher/eosio-launcher"
     MongoPath="mongo"
     ShuttingDown=False
+    CheckOutputDeque=deque(maxlen=10)
 
     @staticmethod
     def Print(*args, **kwargs):
@@ -76,6 +78,7 @@ def checkOutput(cmd):
         assert(isinstance(cmd, list))
         popen=subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         (output,error)=popen.communicate()
+        Utils.CheckOutputDeque.append((output,error))
         if popen.returncode != 0:
             raise subprocess.CalledProcessError(returncode=popen.returncode, cmd=cmd, output=error)
         return output.decode("utf-8")