[crush] Improve error messages.

crush.lua

@@ -214,7 +214,7 @@ local function scandeps(manifest, mode, deps)
         error(def)  -- def is now pcall()'s error message
     end
     if type(def) ~= 'table' then
-        error("[\""..manifest.."\"] loading file resulted in a '"..type(def).."', 'table' expected.")
+        error("[string \""..manifest.."\"]: Loading resulted in a '"..type(def).."', while 'table' was expected.")
     end
 
     for name,url in pairs(def) do
@@ -223,7 +223,7 @@ local function scandeps(manifest, mode, deps)
         end
 
         if type(url) ~= 'string' then
-            error(manifest..": unexpected type "..type(dep).." as "..name.." git repository URL.")
+            error("[string \""..manifest.."\"]: "..name..": git repository URL must be a 'string'.")
         end
 
         for i in ipairs(deps) do
@@ -232,7 +232,7 @@ local function scandeps(manifest, mode, deps)
                     goto skip
                 end
 
-                error(manifest..": Duplicate dependency '"..name.."'.")
+                error("[string \""..manifest.."\"]: "..name..": Duplicate dependency.")
             end
         end