Remove error foo from module

src/module.rs

@@ -1,49 +1,11 @@
 use runtime::Runtime;
-
-pub struct ModuleError {
-    shortdesc : String,
-    longdesc  : String,
-}
-
-impl ModuleError {
-
-    pub fn short(short : String) -> ModuleError {
-        ModuleError::new(short, "".to_string())
-    }
-
-    pub fn new(short : String, long : String) -> ModuleError {
-        ModuleError {
-            shortdesc: short,
-            longdesc: long,
-        }
-    }
-
-    pub fn print(&self, rt : &Runtime) {
-        if self.longdesc.is_empty() {
-            let s = format!("Error: {}\n\n{}\n\n",
-                            self.shortdesc, self.longdesc);
-            rt.print(&s)
-        } else {
-            let s = format!("Error: {}\n", self.shortdesc);
-            rt.print(&s)
-        }
-    }
-
-    pub fn print_short(&self, rt : &Runtime) {
-        rt.print(&self.shortdesc)
-    }
-
-    pub fn print_long(&self, rt : &Runtime) {
-        rt.print(&self.longdesc)
-    }
-
-}
+use std::error::Error;
 
 pub trait Module {
 
     fn load(self, &rt : Runtime) -> Self;
     fn name(self) -> String;
 
-    fn execute(self, &rt : Runtime) -> Option<ModuleError>;
+    fn execute(&self, &rt : Runtime) -> Option<Error>;
 
 }