Support comma delimited string for namedtuple.

[graingert]

from collections import namedtuple

X = namedtuple('X', 'a, b')
x = X(1, 'x')
x = X(b='y', a='x')  # error: Unexpected keyword argument "a" for "X"
x.a + [1]  # error: "X" has no attribute "a"
class Y(X): 
    """you can use a namedtuple class as a base class"""

[The-Compiler]

#529 is the same thing for enum.Enum.

[elazarg]

I will add it to PR #1810, although it's easy enough not to wait for it. It requires a single line change here. Changing items = str_expr.value.split() into items = str_expr.value.replace(',', ' ').split()

However, as discussed in the Enum case, it's a good idea not to use this form.

[elazarg]

This has been be fixed by #1810