Using rm * (wildcard) in envoy: No such file or directory

I'm using Python and Envoy. I need to delete all files in a directory. Apart from some files, the directory is empty. In a terminal this would be:

rm /tmp/my_silly_directory/*

Common sense dictates that in envoy, this translates into:

r = envoy.run('rm /tmp/my_silly_directory/*')

However:

r.std_err -> "rm: cannot remove `/tmp/my_silly_directory/*': No such file or directory"

Naturally there are alternatives to using envoy in this case, I am simply wondering why it doesn't work.

Any clues?