E131: Inconsistent handling of kwarg with binary operator expression as value

[baroquebobcat]

I think pycodestyle's handling of binary operator expressions that are the values of kwargs could be improved.

There is a case that is a little ambiguous to me as to whether it should be a style error or not. Should calls where the binary operator subexpressions are aligned with the = of the kwarg be errors? Currently, this triggers E131.

call(
  kwarg=a +
        b +
        c
)

On the other side, dropping the lines indentation to the same as the kwarg is considered valid, which seems to me to go against the spirit of the pep8 guidelines.

call(
  kwarg=a +
  b +
  c
)