test_smart_open: close gzip obj after writing

[ghost]

Motivation

fixes test_smart_open unit tests when run under python 3.12.

https://hydra.nixos.org/build/257823750
log

=========================== short test summary info ============================
FAILED smart_open/tests/test_smart_open.py::SmartOpenHttpTest::test_http_gz - EOFError: Compressed file ended before the end-of-stream marker was reached
FAILED smart_open/tests/test_smart_open.py::SmartOpenHttpTest::test_http_gz_query - EOFError: Compressed file ended before the end-of-stream marker was reached
FAILED smart_open/tests/test_smart_open.py::test_s3_gzip_compress_sanity - EOFError: Compressed file ended before the end-of-stream marker was reached
FAILED smart_open/tests/test_smart_open.py::test_s3_read_explicit[s3://bucket/gzipped-.gz] - EOFError: Compressed file ended before the end-of-stream marker was reached
FAILED smart_open/tests/test_smart_open.py::test_s3_write_explicit[.gz-\x1f\x8b\x08\x087'\x93`\x02\xffkey\x00] - assert b"\x1f\x8b\x0...3\x00\x00\x00" == b"\x1f\x8b\x0...02\xffkey\x00"
FAILED smart_open/tests/test_smart_open.py::test_s3_write_implicit[s3://bucket/key.gz-.gz-\x1f\x8b\x08\x087'\x93`\x02\xffkey\x00] - assert b"\x1f\x8b\x0...3\x00\x00\x00" == b"\x1f\x8b\x0...02\xffkey\x00"
FAILED smart_open/tests/test_smart_open.py::test_s3_disable_compression[s3://bucket/key.gz-.gz-\x1f\x8b\x08\x087'\x93`\x02\xffkey\x00] - assert b"\x1f\x8b\x0...3\x00\x00\x00" == b"\x1f\x8b\x0...02\xffkey\x00"
= 7 failed, 372 passed, 4 skipped, 4 deselected, 4 xfailed, 2 xpassed, 2412 warnings in 93.89s (0:01:33) =

[ddelange]

does it make sense to add 3.12 to the github test matrix?

[mpenkov]

@ddelange Yes, let me go do that now

[mpenkov]

Thank you @annaleeleaves