Avoid finding submodules for compiled objects, because it's at least not implemented

jedi/inference/imports.py

@@ -365,6 +365,8 @@ class Importer(object):
                 # Non-modules are not completable.
                 if value.api_type != 'module':  # not a module
                     continue
+                if not value.is_compiled():
+                    # sub_modules_dict is not implemented for compiled modules.
                     names += value.sub_modules_dict().values()
 
             if not only_modules: