Add new error type for low-level file system errors

libimagstore/src/error.rs

@@ -10,6 +10,7 @@ use std::io::Error as IOError;
 
 #[derive(Clone, Copy, Debug)]
 pub enum StoreErrorKind {
+    FileError,
     IdLocked,
     IdNotFound,
     OutOfMemory,
@@ -18,6 +19,7 @@ pub enum StoreErrorKind {
 
 fn store_error_type_as_str(e: &StoreErrorKind) -> &'static str {
     match e {
+        &StoreErrorKind::FileError   => "File Error",
         &StoreErrorKind::IdLocked    => "ID locked",
         &StoreErrorKind::IdNotFound  => "ID not found",
         &StoreErrorKind::OutOfMemory => "Out of Memory",