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I found a few possible bugs in tarfile:
- "mode in 'raw'" can give false positives for '' or 'ra'. Most of the code also checks for "len(mode) > 1", but I find clearer and safer to just use "mode in ('r', 'a', 'w')".
- To use the shadowed builtin "open", tarfile uses both "import as" and a local alias "bltin_open = open". However, the second idiom would break if tarfile were reloaded.
- Error messages don’t say what the invalid mode was. (Error messages are not part of the language, but nonetheless maybe it’s best not to commit that to stable branches.)