PyPy's zipimport._zip_directory_cache implementation does not support direct
item assignment, thus breaking our attempts at silently updating the cached zip
archive directory information behind the scene. As a workaround, when using
PyPy, we fall back to simply clearing the stale cached information.

--HG--
extra : amend_source : 991e30244754d8fac042da56ac4cf0ad1a0f50d5

--HG--
extra : rebase_source : beb6c57dfd500432304518b9d313d1a98e2614b9

--HG--
extra : rebase_source : 04b4807ccc7bf95d87797716f5d3488d420fa692

--HG--
rename : setuptools/script template (dev).py => setuptools/script (dev).tmpl
rename : setuptools/script template.py => setuptools/script.tmpl

Now that 2to3 is no longer run on the codebase, it's safe for the templates to be syntactically incorrect (prior to substitution).

This is an extra safety measure to avoid someone holding a reference to this
cached data and using its content even after we know that the underlying zip
archive has been removed and possibly even replaced.

Change suggested by PJ Eby (pje on BitBucket) in a setuptools pull request #51
comment:
  https://bitbucket.org/pypa/setuptools/pull-request/51/diff#comment-2018183

--HG--
extra : rebase_source : 6de2309bc7446647749cfe78ab00e0230a07f92f

_update_zipimporter_cache() extracted from _uncache() &
_replace_zip_directory_cache_data().

Code cleanup done in preparation for adding a bit more detailed cache item
clearing logic, so that would not require adding a separate function with yet
more code duplication.

--HG--
extra : rebase_source : e2e956e042c7cbfabe2c31ecc58a4f76c91f40aa

Extracted code for collecting a list of zipimporter cache entries related to a
given path into _collect_zipimporter_cache_entries().

--HG--
extra : rebase_source : 54ab881d794f95467e811511433a2cd31595339e

--HG--
extra : rebase_source : c8c77d96880275e34c1580991c2d70486b6d0e00

Change-Id: Ic3cc25a02de71b94a08f0bf64e8d8b01b572a23b

--HG--
extra : rebase_source : a49971d71570380f1ef51a88897d72328de337ed

pypy uses a custom zipimport._zip_directory_cache implementation class that
does not support the complete dict interface, e.g. it does not support the
dict.pop() method.

For more detailed information see the following links:
  https://bitbucket.org/pypa/setuptools/issue/202/more-robust-zipimporter-cache-invalidation#comment-10495960
  https://bitbucket.org/pypy/pypy/src/dd07756a34a41f674c0cacfbc8ae1d4cc9ea2ae4/pypy/module/zipimport/interp_zipimport.py#cl-99

--HG--
extra : rebase_source : 95cff7946455f0a4422d97eecab11164a9ddef10