Avoid running Python scripts in the root of the package, as this
triggers `os.listdir` on the Nix store directory during import. This
operation can be time-consuming on large store directories
(see issue #283795 for more details).
The issue was initially fixed in #284153 but was reverted in #306339.
Co-authored-by: Sönke Hahn <soenkehahn@gmail.com>
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