bpo-26067: Do not fail test_shutil / chown when gid/uid cannot be resolved

[MatzeB]

There is no guarantee that the users primary uid or gid can be resolved
in the unix group/account databases. Skip the last part of the chown
test if we cannot resolve the gid or uid to a name.

https://bugs.python.org/issue26067

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[DinoV]

You could do try/except KeyError: pass/else here instead of doing the assignments and None checks.

[MatzeB]

Just wanted to keep the try/except scope as small as possible in case some of the other commands raise. Anyway will change.

[MatzeB]

Oops, just realized what you meant here, re-submitted.

[vstinner]

Suggested change

	- Do not fail test_shutil test_chown test when uid or gid of user cannot be resolved to a name.
	Do not fail test_shutil test_chown test when uid or gid of user cannot be resolved to a name.

[bedevere-bot]

@DinoV: Please replace # with GH- in the commit message next time. Thanks!