[issue26952] argparse help formatter crashes

[paul j3]

paul j3 <ajipanca at gmail.com> added the comment:

Xiang Zhang pointed out that the immediate error in this case was caused by the empty mutually exclusive group:

https://bugs.python.org/issue26952#msg264835

The nesting fails because adding actions to the argument_group does not enroll them in the mutually exclusive group.  So the group._group_actions list remains empty, just as it is in your case.

As I pointed out earlier, the usage formatter is brittle.  The addition of mutually exclusive group markings is particularly clunky.

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<https://bugs.python.org/issue26952>
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