capybara/virtualenv/lib/python2.7/site-packages/setuptools/command/easy_install.py
def _update_zipimporter_cache(normalized_path, cache, updater=None):
    """
    Update zipimporter cache data for a given normalized path.

    Any sub-path entries are processed as well, i.e. those corresponding to zip
    archives embedded in other zip archives.

    Given updater is a callable taking a cache entry key and the original entry
    (after already removing the entry from the cache), and expected to update
    the entry and possibly return a new one to be inserted in its place.
    Returning None indicates that the entry should not be replaced with a new
    one. If no updater is given, the cache entries are simply removed without
    any additional processing, the same as if the updater simply returned None.

    """
    for p in _collect_zipimporter_cache_entries(normalized_path, cache):
        # N.B. pypy's custom zipimport._zip_directory_cache implementation does
        # not support the complete dict interface:
        # * Does not support item assignment, thus not allowing this function
        #    to be used only for removing existing cache entries.
        #  * Does not support the dict.pop() method, forcing us to use the
        #    get/del patterns instead. 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
        old_entry = cache[p]
        del cache[p]
        new_entry = updater and updater(p, old_entry)
        if new_entry is not None:
            cache[p] = new_entry
def _update_zipimporter_cache(normalized_path, cache, updater=None):
    """
    Update zipimporter cache data for a given normalized path.

    Any sub-path entries are processed as well, i.e. those corresponding to zip
    archives embedded in other zip archives.

    Given updater is a callable taking a cache entry key and the original entry
    (after already removing the entry from the cache), and expected to update
    the entry and possibly return a new one to be inserted in its place.
    Returning None indicates that the entry should not be replaced with a new
    one. If no updater is given, the cache entries are simply removed without
    any additional processing, the same as if the updater simply returned None.

    """
    for p in _collect_zipimporter_cache_entries(normalized_path, cache):
        # N.B. pypy's custom zipimport._zip_directory_cache implementation does
        # not support the complete dict interface:
        # * Does not support item assignment, thus not allowing this function
        #    to be used only for removing existing cache entries.
        #  * Does not support the dict.pop() method, forcing us to use the
        #    get/del patterns instead. 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
        old_entry = cache[p]
        del cache[p]
        new_entry = updater and updater(p, old_entry)
        if new_entry is not None:
            cache[p] = new_entry
Update zipimporter cache data for a given normalized path.

    Any sub-path entries are processed as well, i.e. those corresponding to zip
    archives embedded in other zip archives.

    Given updater is a callable taking a cache entry key and the original entry
    (after already removing the entry from the cache), and expected to update
    the entry and possibly return a new one to be inserted in its place.
    Returning None indicates that the entry should not be replaced with a new
    one. If no updater is given, the cache entries are simply removed without
    any additional processing, the same as if the updater simply returned None.