python import_module function not loading package -

i have below openstack rally code dynamically loading python modules given path using below function.

def load_plugins(dir_or_file):    if os.path.isdir(dir_or_file):       directory = dir_or_file       log.info(_("loading plugins directories %s/*") %              directory.rstrip("/"))        to_load = []       root, dirs, files in os.walk(directory, followlinks=true):           to_load.extend((plugin[:-3], root)                          plugin in files if plugin.endswith(".py"))       plugin, directory in to_load:          if directory not in sys.path:             sys.path.append(directory)           fullpath = os.path.join(directory, plugin)          try:             fp, pathname, descr = imp.find_module(plugin, [directory])             imp.load_module(plugin, fp, pathname, descr)             fp.close()             log.info(_("\t loaded module plugins: %s.py") % fullpath)          except exception e:             log.warning(                 "\t failed load module plugins %(path)s.py: %(e)s"                 % {"path": fullpath, "e": e})             if logging.is_debug():                 log.exception(e)    elif os.path.isfile(dir_or_file):       plugin_file = dir_or_file       log.info(_("loading plugins file %s") % plugin_file)       if plugin_file not in sys.path:          sys.path.append(plugin_file)       try:          plugin_name = os.path.splitext(plugin_file.split("/")[-1])[0]          imp.load_source(plugin_name, plugin_file)          log.info(_("\t loaded module plugins: %s.py") % plugin_name)       except exception e:          log.warning(_(             "\t failed load module plugins %(path)s: %(e)s")             % {"path": plugin_file, "e": e})          if logging.is_debug():             log.exception(e) 

this working absolutely fine till 2 days ago. not getting error not loading classes well. first log information printed , getting printed , while looking loaded classes fails. below ensure_plugins_are_loaded internally calling above function.

 file "<decorator-gen-3>", line 2, in _run  file "build/bdist.linux-x86_64/egg/rally/plugins/__init__.py", in    ensure_plugins_are_loaded  file "build/bdist.linux-x86_64/egg/rally/task/engine.py",  in validate 

update 1

i tried calling simple importlib.import_module('/opt/plugins'). still not error thrown import_module python still can't find loaded modules. trying find modules using subs = cls.subclasses() extends given subclass.

update 2

i tried use same code without creating bdist_egg package. did

python setup.py develop

and works fine. not sure problem when using bdist_egg.