Remove std.stdio import and printing of unexpected tokens

assets/parser.d.erb

@@ -3,12 +3,10 @@
  *
  * This file is generated by Propane.
  */
-
 <% if @grammar.modulename %>
-module <%= @grammar.modulename %>;
 
+module <%= @grammar.modulename %>;
 <% end %>
-import std.stdio;
 
 /**************************************************************************
  * User code blocks
@@ -913,16 +911,6 @@ public size_t <%= @grammar.prefix %>parse(<%= @grammar.prefix %>context_t * cont
             continue;
         }
 
-        /* Error, unexpected token. */
-        write("Unexpected token ");
-        if (token != INVALID_TOKEN_ID)
-        {
-            writeln(<%= @grammar.prefix %>token_names[token]);
-        }
-        else
-        {
-            writeln("{other}");
-        }
         /* A token was successfully lexed, so the input text position was
          * advanced. However, this is an unexpected token, so we want to reset
          * the context text position to point to the token rather than the text