Slight tweaks to the error messages.

core/builtin.py

@@ -497,7 +497,7 @@ def Pushd(argv, dir_stack):
  try:
    os.chdir(dest_dir)
  except OSError as e:
    util.error("cd: %r: %s", dest_dir, os.strerror(e.errno))
    util.error("pushd: %r: %s", dest_dir, os.strerror(e.errno))
    return 1

  dir_stack.append(os.getcwd())
@@ -508,13 +508,13 @@ def Popd(argv, dir_stack):
  try:
    dest_dir = dir_stack.pop()
  except IndexError:
    log('popd: directory stack is empty')
    util.error('popd: directory stack is empty')
    return 1

  try:
    os.chdir(dest_dir)
  except OSError as e:
    util.error("cd: %r: %s", dest_dir, os.strerror(e.errno))
    util.error("popd: %r: %s", dest_dir, os.strerror(e.errno))
    return 1

  return 0