RuntimeError: generator raised StopIteration

[jaraco]

I see this error when running Setuptools' tests on Python 3.7:

==================================================================================== FAILURES =====================================================================================
_______________________________________________________________________ TestParsing.testSimpleRequirements ________________________________________________________________________

strs = 'x\\'

    def parse_requirements(strs):
        """Yield ``Requirement`` objects for each specification in `strs`

        `strs` must be a string, or a (possibly-nested) iterable thereof.
        """
        # create a steppable iterator, so we can handle \-continuations
        lines = iter(yield_lines(strs))

        for line in lines:
            # Drop comments -- a hash without a space may be in a URL.
            if ' #' in line:
                line = line[:line.find(' #')]
            # If there is a line continuation, drop it, and append the next line.
            if line.endswith('\\'):
                line = line[:-2].strip()
>               line += next(lines)
E               StopIteration

pkg_resources/__init__.py:3038: StopIteration

The above exception was the direct cause of the following exception:

self = <pkg_resources.tests.test_resources.TestParsing object at 0x1059e1da0>

    def testSimpleRequirements(self):
        assert (
            list(parse_requirements('Twis-Ted>=1.2-1'))
            ==
            [Requirement('Twis-Ted>=1.2-1')]
        )
        assert (
            list(parse_requirements('Twisted >=1.2, \\ # more\n<2.0'))
            ==
            [Requirement('Twisted>=1.2,<2.0')]
        )
        assert (
            Requirement.parse("FooBar==1.99a3")
            ==
            Requirement("FooBar==1.99a3")
        )
        with pytest.raises(ValueError):
            Requirement.parse(">=2.3")
        with pytest.raises(ValueError):
>           Requirement.parse("x\\")

pkg_resources/tests/test_resources.py:600:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

s = 'x\\'

    @staticmethod
    def parse(s):
>       req, = parse_requirements(s)
E       RuntimeError: generator raised StopIteration

pkg_resources/__init__.py:3092: RuntimeError

[jaraco]

The issue is an intentional regression introduced in Python 3.7 as part of PEP 479.

[seekun]

Thanks