return NULL in case some Python function fails

[dirk-thomas]

Follow up of ros2/rclpy#95.

• Linux
• Linux-aarch64
• macOS
• Windows

Ready for review.

[mikaelarguedas]

LGTM, (once CI green)

I was originally curious about how these two functions were identified (in opposition to the other functions that can raise in convert_to_py). @dirk-thomas tested empirically all of them and couldn't reproduce ros2/rclpy#95 once these 2 cases were handled. So I'm in favor of merging this as is, keeping in mind that we will need to replace the remaining asserts and wrap potentially raising function calls properly in a future PR

[dirk-thomas]

in opposition to the other functions that can raise in convert_to_py

Just for the record: they all return error codes - almost none of them raises exceptions.

[mikaelarguedas]

Just for the record: they all return error codes - almost none of them raises exceptions

Yes with a few "exceptions" 😜
I agree only a handful of them can raise all the other ones are "safe"

[dirk-thomas]

I agree only a handful of them can raise all the other ones are "safe"

The problem are not the potential exceptions here. The problem is that some functions return an error code which our code either ignores or asserts on.