FEATURE: Wrap include failures in a Build Error.

This is way more ergonomic for the users.

src/build/mod.rs

@@ -1658,8 +1658,20 @@ impl<'a> FileBuilder<'a> {
                         eprintln!("including an empty file. Use NULL as the result");
                         Rc::new(Val::Empty)
                     } else {
-                        // FIXME(jwall): This should be wrapped in a BuildError
+                        match importer.import(file_contents.as_bytes()) {
-                        importer.import(file_contents.as_bytes())?
+                            Ok(v) => v,
+                            Err(e) => {
+                                let err = Box::new(error::BuildError::with_pos(
+                                    format!(
+                                        "{} include failed for {}",
+                                        &def.typ.fragment, &def.path.fragment
+                                    ),
+                                    error::ErrorType::IncludeError,
+                                    def.pos.clone(),
+                                ));
+                                return Err(err.wrap_cause(e).to_boxed());
+                            }
+                        }
                     };
                     Ok(val)
                 }

src/error.rs

@@ -30,6 +30,7 @@ pub enum ErrorType {
     NoSuchSymbol,
     BadArgLen,
     FormatError,
+    IncludeError,
     ReservedWordError,
     // Parsing Errors
     ParseError,
@@ -47,6 +48,7 @@ impl fmt::Display for ErrorType {
             &ErrorType::NoSuchSymbol => "NoSuchSymbol",
             &ErrorType::BadArgLen => "BadArgLen",
             &ErrorType::FormatError => "FormatError",
+            &ErrorType::IncludeError => "IncludeError",
             &ErrorType::ReservedWordError => "ReservedWordError",
             &ErrorType::ParseError => "ParseError",
             &ErrorType::AssertError => "AssertError",
@@ -93,6 +95,10 @@ impl BuildError {
         self
     }
 
+    pub fn to_boxed(self) -> Box<Self> {
+        Box::new(self)
+    }
+
     fn render(&self, w: &mut fmt::Formatter) -> fmt::Result {
         if let Some(ref pos) = self.pos {
             let file = match pos.file {

src/main.rs

@@ -271,7 +271,7 @@ fn inspect_command(
                     match builder.eval_string(&normalized) {
                         Ok(v) => Some(v.clone()),
                         Err(e) => {
-                            eprintln!("Err: {}", e);
+                            eprintln!("{}", e);
                             process::exit(1);
                         }
                     }