tests/import/import_override: Add .exp file to workaround CPython3.8.
tests/import/import_override: Add .exp file to workaround CPython3.8.

CPython3.8 appears to execute unsolicited imports of _os module when
executing other imports, like "from pkg.mod import foo".

Change-Id: I579f9d19e6417c2c987ee3ffe86c1cfa0ad21ad1
Signed-off-by: Paul Sokolovsky <9dc5061f178bb11813e14f1ed02ba27eaf21fa5d@users.sourceforge.net>

pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython,pfalcon/micropython