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While committing issue #24129, I noticed the following in the execution model documentation:
==================
If a variable is referenced in an enclosing scope, it is illegal to delete the name. An error will be reported at compile time.
==================
I'm not sure what that means, as both of the following compiled fine for me under 3.4.2:
>>> def f():
... x = 1
... def g():
... nonlocal x
... del x
... 
>>> def f():
... x = 1
... del x
... def g():
... print(x)
...

Note that I haven't attempted to resolve this myself, as I'm not sure if we should just delete the paragraph, or if we accidentally dropped a compile time error check that didn't have any tests somewhere along the line.
Probably a good one to raise on python-dev...

I wonder if it is a left-over from the behaviour prior to 3.2? In 3.1, I
get this syntax error:
py> def outer():
... spam = 1
... def inner():
... nonlocal spam
... del spam
... inner()
...
SyntaxError: can not delete variable 'spam' referenced in nested scope
See also the "Changed in 3.2" comment here:
https://docs.python.org/3/reference/simple_stmts.html#the-del-statement 

It looks like it is safe to just remove this line from docs. This code
>>> x = 1
>>> def f():
... global x
... del x
... 
>>> f()
>>> x
Works as expected, i.e. raises NameError. (The same happens for nonlocal but with UnboundLocalError.)

Thanks for the PR, Ivan. Merged and backported to 3.5 and 3.6.