Output last command info on k5test failures

When a k5test failure occurs, display the last executed command, its
command index, and its output.  This will make it easier to understand
"make check" failures when it is not easy to run subsequent commands
or investigate the filesystem of the build host.

src/util/k5test.py

@@ -373,6 +373,11 @@ def fail(msg):
     """Print a message and exit with failure."""
     global _current_pass
     print "*** Failure:", msg
+    if _last_cmd:
+        print "*** Last command (#%d): %s" % (_cmd_index - 1, _last_cmd)
+    if _last_cmd_output:
+        print "*** Output of last command:"
+        sys.stdout.write(_last_cmd_output)
     if _current_pass:
         print "*** Failed in test pass:", _current_pass
     sys.exit(1)
@@ -643,15 +648,16 @@ def _stop_or_shell(stop, shell, env, ind):
 
 
 def _run_cmd(args, env, input=None, expected_code=0):
-    global null_input, _cmd_index, _debug
+    global null_input, _cmd_index, _last_cmd, _last_cmd_output, _debug
     global _stop_before, _stop_after, _shell_before, _shell_after
 
     if (_match_cmdnum(_debug, _cmd_index)):
         return _debug_cmd(args, env, input)
 
     args = _valgrind(args)
+    _last_cmd = _shell_equiv(args)
 
-    output('*** [%d] Executing: %s\n' % (_cmd_index, _shell_equiv(args)))
+    output('*** [%d] Executing: %s\n' % (_cmd_index, _last_cmd))
     _stop_or_shell(_stop_before, _shell_before, env, _cmd_index)
 
     if input:
@@ -663,6 +669,7 @@ def _run_cmd(args, env, input=None, expected_code=0):
     proc = subprocess.Popen(args, stdin=infile, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT, env=env)
     (outdata, dummy_errdata) = proc.communicate(input)
+    _last_cmd_output = outdata
     code = proc.returncode
     output(outdata)
     output('*** [%d] Completed with return code %d\n' % (_cmd_index, code))
@@ -697,7 +704,7 @@ def _debug_cmd(args, env, input):
 # we see sentinel as a substring of a line on either stdout or stderr.
 # Clean up the daemon process on exit.
 def _start_daemon(args, env, sentinel):
-    global null_input, _cmd_index, _debug
+    global null_input, _cmd_index, _last_cmd, _last_cmd_output, _debug
     global _stop_before, _stop_after, _shell_before, _shell_after
 
     if (_match_cmdnum(_debug, _cmd_index)):
@@ -708,15 +715,17 @@ def _start_daemon(args, env, sentinel):
         sys.exit(1)
 
     args = _valgrind(args)
-    output('*** [%d] Starting: %s\n' %
-           (_cmd_index, _shell_equiv(args)))
+    _last_cmd = _shell_equiv(args)
+    output('*** [%d] Starting: %s\n' % (_cmd_index, _last_cmd))
     _stop_or_shell(_stop_before, _shell_before, env, _cmd_index)
 
     # Start the daemon and look for the sentinel in stdout or stderr.
     proc = subprocess.Popen(args, stdin=null_input, stdout=subprocess.PIPE,
                             stderr=subprocess.STDOUT, env=env)
+    _last_cmd_output = ''
     while True:
         line = proc.stdout.readline()
+        _last_cmd_output += line
         if line == "":
             code = proc.wait()
             fail('%s failed to start with code %d.' % (args[0], code))
@@ -1215,6 +1224,8 @@ def cross_realms(num, xtgts=None, args=None, **keywords):
 signal.signal(signal.SIGINT, _onsigint)
 _outfile = open('testlog', 'w')
 _cmd_index = 1
+_last_cmd = None
+_last_cmd_output = None
 buildtop = _find_buildtop()
 srctop = _find_srctop()
 plugins = os.path.join(buildtop, 'plugins')