Simplified reporting

This is branched off of https://github.com/dimagi/commcare-hq/pull/4571 and should not be merged first.
interesting syntax. `lambda` does not require parens around its arguments. Note that surprising things happen if another "argument" is added without removing the parens:
```python
>>> f = lambda(x, y): (x, y)
>>> f(1, 2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: <lambda>() takes exactly 1 argument (2 given)
>>> f((1, 2))
(1, 2)
```