How can I replicate the feature-homography tutorial using the Python API?

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I've been trying to convert the feature-homography tutorial so that I can do the same thing using the Python API but I'm struggling to convert it. Specifically, I've got as far as step 3 but the following call:

matcher = cv2.FlannBasedMatcher()

...results in this:

Traceback (most recent call last):
  File "/Users/jon/PycharmProjects/LeccyReader/WebcamReader.py", line 244, in <module>
    search_image(img_object, img_scene)
  File "/Users/jon/PycharmProjects/LeccyReader/WebcamReader.py", line 155, in search_image
    matcher = cv2.FlannBasedMatcher()
SystemError: null argument to internal routine