Closes #18807: pyvenv now takes a --copies argument allowing copies instead of symlinks even where symlinks are available and the default.

The return value of close() is not always a toplevel element. It depends on
what the underlying target returns. By default, TreeBuilder returns the
toplevel document element.

(grafted from 23181bf411a16287a0a54e910fc0f9ecd2764bf0)

Patch by Michele Orrù.

Do we need a fallback implementation of getcwd() from 1991 that claims to
support "really old Unix systems"? I don't think so.

Patch by Stefan Behnel.

#18796: improve documentation of the file argument of dis.show_code.  Initial patch by Vajrasky Kok.

caches.

Eliminates the ResoureWarning raised during testing.

Patch also independently written by Vajrasky Kok.

context when raising a new KeyError with the original key.

when raising a new KeyError with the original key.

multiple times.

With importlib getting used more and more, changing __import__ will
not work as well as people used to hope as it will potentially bypass
importers, etc. It also will not work with importlib.import_module()
as it uses "importlib.__import__" (i.e. importlib's implementation of
import) directly and not builtins.__import__.

(grafted from 1ea833ecaf5a9d43a886e9e73b4e2551d0d5b548)

It suffices to keep just one reference when the object is created.