Consistent use of "return None" in functions

Could you add this rule to pep8? I just updated the official PEP 8 to include this (I'm surprised it wasn't already there):

• Be consistent in return statements. Either all return statements in a
  function should return an expression, or none of them should. If any return
  statement returns an expression, any return statements where no value is
  returned should explicitly state this as return None, and an explicit
  return statement should be present at the end of the function (if
  reachable).

   Yes:

   def foo(x):
       if x >= 0:
           return math.sqrt(x)
       else:
           return None

   def bar(x):
       if x < 0:
           return None
       return math.sqrt(x)

   No:

   def foo(x):
       if x >= 0:
           return math.sqrt(x)

   def bar(x):
       if x < 0:
           return
       return math.sqrt(x)

https://mail.python.org/pipermail/python-dev/2015-April/139054.html

Start by locating the pycodestyle implementation and its tests, then compare the current behavior with the quoted PEP 8 examples. Done means the checker enforces the shown Yes/No return-statement distinctions and the relevant regression coverage passes.