[issue21751] Expand zipimport to support bzip2 and lzma

[Nick Coghlan]

Nick Coghlan added the comment:

Another use case is more aggressively shrinking the bundled copy of pip. We
don't really care about speed of execution there (since we only run it
directly once at install time to do the bootstrapping), but we do care
about the impact on the installer size.

However, that's a fairly specialised case - for wheel 2.0 in general, we
can consider dropping the "always usable as a sys.path entry" behaviour and
not need to worry about the constraints of zipimport (which has indeed
exhibited unfortunate "we touch it, we break it" behaviour in recent
releases, due to the vagaries of zip implementations on various platforms).

A more general archive importer written in Python could also be useful -
there's no requirement that all archive formats be handled by the existing
meta importer. Putting such an importer *after* the existing zip importer
in the metapath would minimise any risk of backwards incompatibility
issues, and allow it to initially be created as a third party module on
PyPI.

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