The config now prints a way better error message if you give it a bad file to use.

config.cpp

@@ -8,7 +8,10 @@ using fmt::format;
 std::filesystem::path Config::BASE_DIR{"."};
 
 Config::Config(const std::string src_path) : $src_path(src_path) {
-  std::ifstream infile(Config::path_to($src_path));
+  auto path_to = Config::path_to($src_path);
+  dbc::check(std::filesystem::exists(path_to),
+      fmt::format("requested config file {} doesn't exist", path_to.string()));
+  std::ifstream infile(path_to);
   $config = json::parse(infile);
 }