Merge branch 'maint'

* maint:
  tests: fix a spurious failure when $PYTHON is in the environment
  python tests: support PEP-3147 installation layout
  python: uninstall cater to PEP-3147
  tests: improve a comment
  tests: honour $PYTHON override
  tests: typofix in message
  news: document fix for bug#8847 (PEP-3147, __pycache__)
  python: improve support for modern python (CPython 3.2 and PyPy)

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>

diff --cc NEWS
Simple merge

diff --cc lib/am/python.am
Simple merge

diff --cc t/ax/am-test-lib.sh
Simple merge

diff --cc t/list-of-tests.mk
Simple merge

diff --cc t/nobase-python.sh
Simple merge

diff --cc t/py-compile-basedir.sh
Simple merge

diff --cc t/py-compile-basic.sh
Simple merge

diff --cc t/py-compile-destdir.sh
Simple merge

diff --cc t/py-compile-option-terminate.sh
Simple merge

diff --cc t/python-pr10995.sh
Simple merge

diff --cc t/python-too-old.sh
Simple merge

diff --cc t/python-vars.sh
Simple merge

diff --cc t/python-virtualenv.sh
Simple merge

diff --cc t/python10.sh
Simple merge

diff --cc t/python11.sh
index e3e29e5,a22826c..a648c7b
--- 1/t/python11.sh
--- 2/t/python11.sh
+++ b/t/python11.sh
@@@ -17,8 -17,11 +17,11 @@@
  # Test missing python.
  
  # Python is not required for this test.
 -. ./defs || exit 1
 +. test-init.sh
  
+ # We don't want to allow user overrides in this test.
+ PYTHON=; unset PYTHON
+ 
  cat >>configure.ac <<'EOF'
  m4_define([_AM_PYTHON_INTERPRETER_LIST], [IShouldNotExist1 IShouldNotExist2])
  AM_PATH_PYTHON

diff --cc t/python12.sh
Simple merge

diff --cc t/python3.sh
Simple merge