ircd::mods: Perform checks before entering boost::dll to avoid obscure error messages.

fixes #80

ircd/mods.cc

@@ -1048,13 +1048,25 @@ ircd::mods::info(const string_view &p,
                  F&& closure)
 try
 {
+	const bool relative
+	{
+		fs::is_relative(p)
+	};
+
 	const auto path
 	{
-		fs::is_relative(p)?
+		relative?
 			fs::_path(fullpath(p)):
 			fs::_path(p)
 	};
 
+	// Check stuff first to avoid obscure errors generated by boost::dll
+	if(!relative && !fs::exists(p))
+		throw fs::error
+		{
+			make_error_code(std::errc::no_such_file_or_directory), "`%s'", p
+		};
+
 	boost::dll::library_info info
 	{
 		path