[issue28449] tarfile.open(mode = 'r:*', ignore_zeros = True) has 50% chance failed to open compressed tars?

[Silver Fox]

New submission from Silver Fox:

Seems all `tarfile.open` will try all compress method(including `raw`) in random order, and `ignore_zeros` also hide the error during detecting compress method. So `raw` is used if tested before the rigth compress method, which is wrong.

But there is no warning that the 2 args can not be used together in docs.

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components: Library (Lib)
messages: 278711
nosy: Silver Fox
priority: normal
severity: normal
status: open
title: tarfile.open(mode = 'r:*', ignore_zeros = True) has 50% chance failed to open compressed tars?
type: behavior
versions: Python 3.4, Python 3.5

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue28449>
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