When importing a set definition file all spaces are removed from the source_file field. This causes issues if a pg file genuinely has spaces in the filename as the imported set will not have the correct source_file.

To reproduce:

1. Create a pg file with a space in the filename and add it to a set.
2. Export the set. The .def file will include the spaces in the filename.
3. Import the set into a course. The spaces have been removed from the filename, and the Set Detail page will report that the source file can't be found (unless there happens to be a file with same name with no spaces).

This looks to be done deliberately: