我将engine_py3重新命名为engine后，不工作了！python转为了系统的py2。
必须重新初始化venv环境。例如
python3.8 -m venv env
这是因为，路径被写进去了。
./pyftmerge:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
./f2py3:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
./activate.fish:set -gx VIRTUAL_ENV "/home/netro/codes/chao_dev/engine_py3/env"
./activate:VIRTUAL_ENV="/home/netro/codes/chao_dev/engine_py3/env"
./hyper:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
./ttx:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
./pyrsa-verify:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
./futurize:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
./activate.csh:setenv VIRTUAL_ENV "/home/netro/codes/chao_dev/engine_py3/env"
./pyrsa-sign:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
./fixup_translate_v3beta1_keywords.py:#!/home/netro/codes/chao_dev/engine_py3/env/bin/python3.8
可见activate中写死了路径。
改变后，找不到了。有些stupid。可以用链接，例如 ln -s engine_py3 engine。可以work