Not having spaces or other non alphanumeric characters in the image file name would prevent this bug from occurring, but not fix it. For usability the importer module should be able to handle any filename that an image could have.

Using URLs as the path to the images opens this URL-encoding can of worms. Using a file path avoids it.

The initial problem wasn't with URL encoding, it was that the exporter exported relative file paths and the importer expected absolute file paths. I'd prefer file paths instead of URLs.

-C