If it fails because the file doesn't exist:
[Open_File_Error#2] Unable to open "foo.file". File not found.
If it does exist and the flags are simple (.Read, .Write or both), it'll say this:
[Open_File_Error#2] Unable to open "foo.file" with perms 0o444 as read-only
It it does exist but fails to open for other reasons, it'll print:
[Open_File_Error#2] Unable to open "foo.file" with perms 0o444 and flags File_Flags{....}
Future work: Translate permissions from octal to `ls -al` format (e.g. `-rwxrwxrwx`).