lack of error checking in ec_file_transfer() causes bad behavior

The ec_file_transfer() function in file.module does no error checking.

If there are any problems downloading the file, it behaves badly. For instance, if the file cannot be opened due to permissions, the download appears to hang, timeout after a while, and results in an empty download.

Even worse, if a problem occurs partway through a download (the fread() fails) the user could end up with a partial file and no notice that a problem occurred.

Recommended fix is to check the return codes of fopen() and fread().

I'd offer a patch, but I'm not sure what the preferred behavior would be if the system call fails. Any suggestions? Is there some function I can call to display a nice error message?