## Summary
This is an attempt to improve the error message for something like
```py
a = 1
def f(a):
global a
```
I realize that the previous wording ("name 'a' is parameter and global")
is used by CPython itself, but unless we are trying to be consistent
with CPython, I think we can improve upon this? The previous version
seemed a bit cryptic to me when I first saw it.
## Test Plan
Updated snapshot tests
David Peter
cf14481f44