It's not a Python 3.8 regression. Python 3.7 has the same behavior.


cd $HOME
python3.7 -m venv testenv
cd testenv/
. bin/activate

wget https://www.python.org/ftp/python/3.8.0/Python-3.8.0rc1.tar.xz
tar -xf Python-3.8.0rc1.tar.xz && cd Python-3.8.0rc1
CC=clang ./configure --prefix=/tmp/python3.host --with-system-ffi --disable-ipv6 --without-ensurepip --with-c-locale-coercion --disable-shared && make

Python 3.8 error:

"""
$ make
./python -E -S -m sysconfig --generate-posix-vars ;\
if test $? -ne 0 ; then \
	echo "generate-posix-vars failed" ; \
	rm -f ./pybuilddir.txt ; \
	exit 1 ; \
fi
Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = './python'
  isolated = 0
  environment = 0
  user site = 1
  import site = 0
  sys._base_executable = '/home/vstinner/testenv/Python-3.8.0rc1/python'
  sys.base_prefix = '/tmp/python3.host'
  sys.base_exec_prefix = '/tmp/python3.host'
  sys.executable = '/home/vstinner/testenv/Python-3.8.0rc1/python'
  sys.prefix = '/tmp/python3.host'
  sys.exec_prefix = '/tmp/python3.host'
  sys.path = [
    '/tmp/python3.host/lib/python38.zip',
    '/tmp/python3.host/lib/python3.8',
    '/tmp/python3.host/lib/lib-dynload',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007ff6a75f6740 (most recent call first):
<no Python frame>
generate-posix-vars failed
make: *** [Makefile:592: pybuilddir.txt] Error 1
"""


cd ..
wget https://www.python.org/ftp/python/3.7.4/Python-3.7.4.tar.xz
tar -xf Python-3.7.4.tar.xz 
cd Python-3.7.4/
CC=clang ./configure --prefix=/tmp/python3.host --with-system-ffi --disable-ipv6 --without-ensurepip --with-c-locale-coercion --disable-shared

Python 3.7 error:

"""
$ make
./python -E -S -m sysconfig --generate-posix-vars ;\
if test $? -ne 0 ; then \
	echo "generate-posix-vars failed" ; \
	rm -f ./pybuilddir.txt ; \
	exit 1 ; \
fi
Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
Fatal Python error: initfsencoding: Unable to get the locale encoding
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f5a77f5a740 (most recent call first):
/bin/sh : ligne 5 : 19592 Aborted                 (core dumped)./python -E -S -m sysconfig --generate-posix-vars
generate-posix-vars failed
make: *** [Makefile:606: pybuilddir.txt] Error 1
"""