prevent croaking if url contains invalid (unquoted) characters

Hey again,

we recently experienced this problem reg. charset encoding in production when receiving invalid characters via URL:

```stacktrace
  File "/Users/amo/.buildout/eggs/Paste-1.7.5.1-py2.7.egg/paste/translogger.py", line 68, in __call__
    return self.application(environ, replacement_start_response)
  File "/Users/amo/.buildout/eggs/repoze.debug-1.0-py2.7.egg/repoze/debug/responselogger.py", line 43, in __call__
    self.log_request_begin(request_id, request_info)
  File "/Users/amo/.buildout/eggs/repoze.debug-1.0-py2.7.egg/repoze/debug/responselogger.py", line 125, in log_request_begin
    self.verbose_logger and self.verbose_logger.info('\n'.join(out))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 66: ordinal not in range(128)
```

This PR accounts for that. Don't know if the fix is solid, though, but works for us.

Cheers,
Andreas.