Add diagnostics in can an item is run multiple times

gclient_utils.py

 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Generic utils."""
 
 import errno
 import logging
 import os
 import Queue
@@ skipping 314 matching lines @@
     filter_fn: A function taking a single string argument called with each line
                of the subprocess2's output. Each line has the trailing newline
                character trimmed.
     stdout: Can be any bufferable output.
 
   stderr is always redirected to stdout.
   """
   assert print_stdout or filter_fn
   stdout = stdout or sys.stdout
   filter_fn = filter_fn or (lambda x: None)
-  assert not 'stderr' in kwargs
   kid = subprocess2.Popen(
       args, bufsize=0, stdout=subprocess2.PIPE, stderr=subprocess2.STDOUT,
       **kwargs)
 
   # Do a flush of stdout before we begin reading from the subprocess2's stdout
   stdout.flush()
 
   # Also, we need to forward stdout to prevent weird re-ordering of output.
   # This has to be done on a per byte basis to make sure it is not buffered:
   # normally buffering is done for each line, but if svn requests input, no
@@ skipping 235 matching lines @@
     running = self.running
     self.running = []
     for t in running:
       if t.isAlive():
         self.running.append(t)
       else:
         t.join()
         sys.stdout.full_flush()  # pylint: disable=E1101
         if self.progress:
           self.progress.update(1, t.item.name)
-        assert not t.item.name in self.ran
+        if t.item.name in self.ran:
+          raise Error(
+              'gclient is confused, "%s" is already in "%s"' % (
+                t.item.name, ', '.join(self.ran)))
         if not t.item.name in self.ran:
           self.ran.append(t.item.name)
 
   def _run_one_task(self, task_item, args, kwargs):
     if self.jobs > 1:
       # Start the thread.
       index = len(self.ran) + len(self.running) + 1
       new_thread = self._Worker(task_item, index, args, kwargs)
       self.running.append(new_thread)
       new_thread.start()
@@ skipping 26 matching lines @@
         logging.info('Caught exception in thread %s' % self.item.name)
         logging.info(str(sys.exc_info()))
         work_queue.exceptions.put(sys.exc_info())
       logging.info('Task %s done' % self.item.name)
 
       work_queue.ready_cond.acquire()
       try:
         work_queue.ready_cond.notifyAll()
       finally:
         work_queue.ready_cond.release()