The following code causes refleaks:
import zipimport
zi = zipimport.zipimporter.__new__(zipimport.zipimporter)
zi.__init__('bar.zip')
zi.__init__('bar.zip')
zi.__init__('bar.zip\\foo')

This is because zipimport_zipimporter___init___impl() (in Modules/zipimport.c)
doesn't decref (if needed) before assigning to `self->files`, `self->archive`
and `self->prefix`.

I would open a PR to fix this soon.

Should i add a test to test_zipimport?
If yes, could you point out some similar refcount test to help me write this
test?

New changeset c0cabc23bbe474d542ff8a4f1243f4ec3cce5549 by Victor Stinner (Oren Milman) in branch 'master':
bpo-31723: Fix refleaks when zipimporter.__init__() is called more than once (GH-3919)
https://github.com/python/cpython/commit/c0cabc23bbe474d542ff8a4f1243f4ec3cce5549

> The following code causes refleaks:

I'm curious, how did you find this code? Are you using a code generator coupled with a tool to track for reference leaks?

I merged your PR, thanks! As I wrote on the PR:

I don't think that a NEWS entry is needed, since you are not supposed to call __init__() multiple times.

I don't think that it's worth it to backport the fix to Python 2.7 and 3.6. So I close the issue.

> I'm curious, how did you find this code? Are you using a code generator coupled with a tool to track for reference leaks?

Oh, I think that the issue is related to bpo-31718.

Yes, i am going manually over the code to find similar stuff to #31718,
and i afraid i found quite a few, and still working on it..