The following code works fine when I run it on OSX 10.9, but causes a segmentation fault when run on linux. Specifically, the Travis build on python 3.5.2 results in a segfault when the last line is uncommented.

import argparse
parser = argparse.ArgumentParser()
group = parser.add_argument_group("Colorspace options")
group.add_mutually_exclusive_group()

This code also works fine when I run it myself on python 3.5.1 on an SL6 machine, so it's either specific to 3.5.2 or it's very platform-specific.

Cannot reproduce this either on stock 3.5.2 or 3.6 on Ubuntu.

I can't reproduce it with 3.5.2 on SL6 either. So it must be a weird issue specific to whatever environment they're using for builds on Travis. I'll close this and submit it as a bug over there.