Thomas,
Sorry to hear that you hit this. In a variety of circumstances, there was a bug which prevented the user-selected IDE from being launched, or IDLE which is shipped with Pro. I believe you're enrolled in the EAP program, and the latest Pro 2.3 candidates should have resolved these issues. If you configure an IDE, it should be used everywhere, including when editing script validation code. If you don't have an IDE selected, it should default to IDLE for all Python scripts now.
The other suggestions in this thread are also good, and if you have further issues with using an IDE of your choice (or the default IDLE), please let me know.
Thanks,
Shaun