Trying to open non app.py file results in a file picker showing up

[rzhao271]

Testing #280

On Windows, I renamed the root-level app.py to haha.py, and typed haha.py when prompted for a path to use. After I pressed enter, I expected a launch.json file that pointed to haha.py, but a file picker opened instead.

[rzhao271]

A file picker still opens, but at least I can pick the haha.py Python file now.

Edit: Using the absolute path works!