It turns out that Webots doesn't (yet) support Python 3.9

The current development version does, which is why the docs say
that it's supported, however the latest release doesn't yet have
that support.

Author: PeterJCLaw

simulator/index.md

@@ -22,9 +22,9 @@ You will also need Python installed.
 
 | Platform | Supported Python Version |
 |----------|--------------------------|
-| Windows  | >= 3.7 (64-bit)          |
-| macOS    | >= 3.7                   |
-| Linux    | >= 3.7                   |
+| Windows  | 3.7 - 3.8 (64-bit)       |
+| macOS    | 3.7 - 3.8                |
+| Linux    | 3.7 - 3.8                |
 
 In the competition, Python 3.7 will be used.