setup.py was trying to build _weakref which is redundant as it's a built-in

module.

Closes issue #9848. Thanks to Arfrever Frehtes Taifersar Arahesis for the bug
report.

Misc/NEWS

@@ -183,6 +183,9 @@ Tests
 Build
 -----
 
+- Issue #9848: Stopping trying to build _weakref in setup.py as it is a
+  built-in module.
+
 - Issue #9806: python-config now has an ``--extension-suffix`` option that
   outputs the suffix for dynamic libraries including the ABI version name
   defined by PEP 3149.

setup.py

@@ -456,9 +456,6 @@ class PyBuildExt(build_ext):
         # on pretty much any POSIXish platform.
         #
 
-        # Some modules that are normally always on:
-        exts.append( Extension('_weakref', ['_weakref.c']) )
-
         # array objects
         exts.append( Extension('array', ['arraymodule.c']) )
         # complex math library functions