don't rmtree() if directory doesn't exist

Drop test for tracing and inline coroutine creation

16: Warn for specific thread module methods r=ltratt a=nanjekyejoannah

Dont merge until python#13  and  python#14 are merged, some helper code cuts across.

This replaces python#15 

Threading module Notes

Python 2:

```
>>> from thread import get_ident
>>> from threading import get_ident
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: cannot import name get_ident
>>> import threading
>>> from threading import _get_ident
>>>
```

Python 3:

```
>>> from threading import get_ident
>>> from thread import get_ident
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'thread'
>
```

**Note:**

There is no neutral way of porting

Co-authored-by: Joannah Nanjekye <[email protected]>

API documentation.

Closes python#16

Lazy globals