Traceback in FTW on download error (404)

When download in the FTW fails, the traceback below has been reported.
First of all a 404 shouldn't be possible in FTW since we should make sure the links work!
The actual traceback should be caught, but the ConnectionException isn't imported in the file...

    File
"D:\OpenLP_Development\OpenLP_Code\2.1\openlp\core\ui\firsttimeform.py", line
436, in _get_file_size
    File "c:\Python33\lib\urllib\request.py", line 156, in urlopen
    File "c:\Python33\lib\urllib\request.py", line 475, in open
    File "c:\Python33\lib\urllib\request.py", line 587, in http_response
    File "c:\Python33\lib\urllib\request.py", line 513, in error
    File "c:\Python33\lib\urllib\request.py", line 447, in _call_chain
    File "c:\Python33\lib\urllib\request.py", line 595, in http_error_default
urllib.error.HTTPError: HTTP Error 404: Not Found

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
    File
"D:\OpenLP_Development\OpenLP_Code\2.1\openlp\core\ui\firsttimeform.py", line
334, in on_current_id_changed
    File
"D:\OpenLP_Development\OpenLP_Code\2.1\openlp\core\ui\firsttimeform.py", line
491, in _pre_wizard
    File
"D:\OpenLP_Development\OpenLP_Code\2.1\openlp\core\ui\firsttimeform.py", line
439, in _get_file_size
NameError: global name 'ConnectionException' is not defined