Could it be that some empty dict magically gets populated from somewhere
invisible?

It's a magical switcher that needs argv[0], which we don't provide.

Closes #103.

Ansible's PluginLoader makes up bullshit when it imports a module
(mostly because it has to make up something), therefore we ended up with
duplicate copies of ansible_mitogen loaded: one under
ansible.plugins.*.mitogen, and one under the canonical namespace.

Which broke isinstance().

Need a more general solution to littering the code with this crap.