Bug#915179: hovercraft FTBFS with Python 3.7

[Adrian Bunk <bunk@debian.org>]

Source: hovercraft
Version: 2.1-3
Severity: serious
Tags: ftbfs

https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/hovercraft.html

...
=================================== FAILURES ===================================
______________________ CalculateTests.test_absolute_path _______________________

positions = [{'data-x': 'r0', 'data-y': 'r0', 'is_path': True, 'path': 'M 100 100 L 300 100 L 300 300'}, {'is_path': True}, {'is_path': True}, {'is_path': True}, {'is_path': True}]

    def calculate_positions(positions):
        """Calculates position information"""
        current_position = {'data-x': 0,
                            'data-y': 0,
                            'data-z': 0,
                            'data-rotate-x': 0,
                            'data-rotate-y': 0,
                            'data-rotate-z': 0,
                            'data-scale': 1,
                            }
    
        positer = iter(positions)
        position = next(positer)
        _update_position(current_position, position)
    
        while True:
    
            if 'path' in position:
                # Start of a new path!
                path = position['path']
                # Follow the path specification
                first_point = _pos_to_cord(current_position)
    
                # Paths that end in Z or z are closed.
                closed_path = path.strip()[-1].upper() == 'Z'
                path = parse_path(path)
    
                # Find out how many positions should be calculated:
                count = 1
                last = False
                deferred_positions = []
                while True:
                    try:
                        position = next(positer)
                        deferred_positions.append(position)
                    except StopIteration:
                        last = True  # This path goes to the end
                        break
                    if not position.get('is_path') or 'path' in position:
                        # The end of the path, or the start of a new one
                        break
                    count += 1
    
                if count < 2:
                    raise AssertionError("The path specification is only used for "
                                         "one slide, which makes it pointless.")
    
                if closed_path:
                    # This path closes in on itself. Skip the last part, so that
                    # the first and last step doesn't overlap.
                    endcount = count + 1
                else:
                    endcount = count
    
                multiplier = (endcount * DEFAULT_MOVEMENT) / path.length()
                offset = path.point(0)
    
                path_iter = iter(deferred_positions)
                for x in range(count):
    
                    point = path.point(x / (endcount - 1))
                    point = ((point - offset) * multiplier) + first_point
    
                    current_position.update(_coord_to_pos(point))
    
                    rotation = _path_angle(path, x / (endcount - 1))
                    current_position['data-rotate-z'] = rotation
                    yield current_position.copy()
>                   position = next(path_iter)
E                   StopIteration

hovercraft/position.py:189: StopIteration

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

self = <hovercraft.tests.test_position.CalculateTests testMethod=test_absolute_path>

    def test_absolute_path(self):
        # Position slides along a path
        positions = [
            {'data-x': 'r0', 'data-y': 'r0', 'path': 'M 100 100 L 300 100 L 300 300',
             'is_path': True},
            {'is_path': True},
            {'is_path': True},
            {'is_path': True},
            {'is_path': True},
        ]
    
>       positions = list(calculate_positions(positions))
E       RuntimeError: generator raised StopIteration

hovercraft/tests/test_position.py:209: RuntimeError
...