Add test fix for library classes being visible to non-dependent plugins

api/src/main/java/net/md_5/bungee/api/plugin/PluginClassloader.java

@@ -63,7 +63,13 @@ final class PluginClassloader extends URLClassLoader
     {
         try
         {
-            return super.loadClass( name, resolve );
+            Class<?> result = super.loadClass( name, resolve );
+
+            // SPIGOT-6749: Library classes will appear in the above, but we don't want to return them to other plugins
+            if ( checkOther || result.getClassLoader() == this )
+            {
+                return result;
+            }
         } catch ( ClassNotFoundException ex )
         {
         }