Updater: unclosed file object

[jku]

file_object in Updater._get_metadata_file() is left unclosed whenever an exception is raised (when the metadata fails a check of any kind). There are loads of examples in the test suite, e.g.

python3 test_updater.py TestUpdater.test_3__update_metadata

will complain "ResourceWarning: unclosed file"

This is not very dangerous but makes it hard to find actual issues in test output (try running all test_updater.py tests). There may be other sources of this warning but the vast number of warnings from this one make it difficult to find them.

[joshuagl]

Seems like a good place to use finally as a clean up handler.

[joshuagl]

Fixed in #1147