isort no-lines-before incorrect in presence of preceding empty sections

[bluetech]

Version: 0.0.251

Consider imports such as

from __future__ import print  # future
from django import db         # third-party
from . import y               # local-folder

and isort config no-lines-before = ["local-folder"].

Expected behavior is:

from __future__ import print  # future

from django import db         # third-party

from . import y               # local-folder

Even though we specified no lines before local-folder, there should still be a line before in this case, because the first-party section which comes between local-folder and third-party isn't included in no-lines-before. This is what isort does.

Actual behavior:

from __future__ import print  # future

from django import db         # third-party
from . import y               # local-folder