Added a check for cases when the HTTP Error does not hold a 'reason' attribute

In such cases the script throws an error and exits without finishing further downloads
Fixed indentation
Merge pull request #108 from swechha/master

Add check for HTTPErrors without a 'reason' attribute to the native downloader.

For example, HTTP Error 403 does not have a 'reason' attribute, in this case the script would throw an exception and stop further downloads.