Vendor untangle and pydevd

[int19h]

You'll probably want to look at just the first two individual commits here, so that you don't have to scroll past all the pydevd code.

@stevdo, @brettcannon - I'm doing some unspeakable things here to package up pydevd as is (so that we can easily merge changes from upstream, and later push them back). It seems to work fine, but please take a look, in case there's some corner case here that I'm missing.

I think that adding a subpath to sys.path should work reliably even with eggs etc, but I wonder if there's any case where just mucking around with paths won't work, and I need an import hook and pkg_resources instead.

[zooba]

That all looks fine. There shouldn't be a need to use any import hooks, but it might be worthwhile importing all the top-level packages from the pydevd folder eagerly and then removing the sys.path entry. (Submodule imports don't rely on sys.path)

I'd also make that assert 'pydevd' not in sys.modules check a proper message explaining what is wrong. Inevitably someone is going to hit it, and the more useful info we can provide the better.

[zooba]

Also, can you email me details of where untangle came from so I can register it in our OSS system?

[brettcannon]

Maybe I missed the discussion, but why do we need to vendor pydevd?

[int19h]

I cleaned up pydevd import as suggested, so that we don't leave anything in sys.path.