Make printing limbo lines in test_sky only print the prefix once.

sky/tools/webkitpy/layout_tests/port/driver.py

 # Copyright (C) 2011 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 433 matching lines @@
         if line and line.endswith("#EOF\r\n"):
             _log.error("Got a CRLF-terminated #EOF - this is a driver bug.")
             return line[:-6], True
         return line, False
 
     def _read_block(self, deadline, is_first_block=False, wait_for_stderr_eof=False):
         block = ContentBlock()
         out_seen_eof = False
 
         have_seen_begin = not is_first_block
+        have_printed_stdout_limbo_line = False
+        have_printed_stderr_limbo_line = False
 
         while not self.has_crashed():
             if out_seen_eof and (self.err_seen_eof or not wait_for_stderr_eof):
                 break
 
             if self.err_seen_eof:
                 out_line = self._server_process.read_stdout_line(deadline)
                 err_line = None
             elif out_seen_eof:
                 out_line = None
                 err_line = self._server_process.read_stderr_line(deadline)
             else:
                 out_line, err_line = self._server_process.read_either_stdout_or_stderr_line(deadline)
 
             if not have_seen_begin:
                 # FIXME(sky): Instead of logging, this should cause the previous test to fail.
                 if err_line:
-                    _log.error('Saw a stderr line between the end of the previous test and the start of the current one: %s' % (
-                        err_line))
+                    if not have_printed_stdout_limbo_line:
+                        have_printed_stdout_limbo_line = True
+                        _log.error('\nSaw a stderr lines between the end of the previous test and the start of the current one:')
+                    _log.error(err_line)
                 if out_line:
                     if out_line == '#BEGIN\n':
                         have_seen_begin = True
                         out_line = ''
                         block.content = ''
                     else:
-                        _log.error('Saw a stdout line between the end of the previous test and the start of the current one: %s' % (
-                            out_line))
+                        if not have_printed_stdout_limbo_line:
+                            have_printed_stdout_limbo_line = True
+                            _log.error('\nSaw a stdout line between the end of the previous test and the start of the current one:')
+                        _log.error(out_line)
 
             if self._server_process.timed_out or self.has_crashed():
                 break
 
             if out_line:
                 assert not out_seen_eof
                 out_line, out_seen_eof = self._strip_eof(out_line)
             if err_line:
                 assert not self.err_seen_eof
                 err_line, self.err_seen_eof = self._strip_eof(err_line)
@@ skipping 34 matching lines @@
         self.decoded_content = None
         self.malloc = None
         self.js_heap = None
         self.stdin_path = None
 
     def decode_content(self):
         if self.encoding == 'base64' and self.content is not None:
             self.decoded_content = base64.b64decode(self.content)
         else:
             self.decoded_content = self.content