only append search paths on first PackageNotFound

Signed-off-by: Lucas Walter <wsacul@gmail.com>

ament_index_cpp/src/get_package_prefix.cpp

@@ -23,11 +23,20 @@
 namespace ament_index_cpp
 {
 
+static size_t package_not_found_count = 0;
+
 static
 std::string
 format_package_not_found_error_message(const std::string & package_name)
 {
-  std::string message = "package '" + package_name + "' not found, searching: [";
+  std::string message = "package '" + package_name + "' not found";
+
+  // Don't need to print out the package paths more than once
+  if (package_not_found_count++ > 0) {
+    return message;
+  }
+
+  message += ", searching: [";
   auto search_paths = get_search_paths();
   for (const auto & path : search_paths) {
     message += path + ", ";