pyenvについて、ここに記述してください。

https://www.python.org/downloads/release/python-385/

$ pyenv install 3.8.5

再開
{{{
$ pyenv install 3.8.5
Downloading Python-3.8.5.tar.xz...
-> https://www.python.org/ftp/python/3.8.5/Python-3.8.5.tar.xz
Installing Python-3.8.5...
WARNING: The Python bz2 extension was not compiled. Missing the bzip2 lib?
WARNING: The Python readline extension was not compiled. Missing the GNU readline lib?
ERROR: The Python ssl extension was not compiled. Missing the OpenSSL lib?

Please consult to the Wiki page to fix the problem.
https://github.com/pyenv/pyenv/wiki/Common-build-problems


BUILD FAILED (Ubuntu 20.04 using python-build 1.2.20-5-g1ec3c6f1)

Inspect or clean up the working tree at /tmp/python-build.20200909094635.49997
Results logged to /tmp/python-build.20200909094635.49997.log

Last 10 log lines:
fi
Looking in links: /tmp/tmpy4xj5ggz
Processing /tmp/tmpy4xj5ggz/setuptools-47.1.0-py3-none-any.whl
Processing /tmp/tmpy4xj5ggz/pip-20.1.1-py2.py3-none-any.whl
Installing collected packages: setuptools, pip
  WARNING: The script easy_install-3.8 is installed in '/home/tmaeno/.pyenv/versions/3.8.5/bin' which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.
  WARNING: The scripts pip3 and pip3.8 are installed in '/home/tmaeno/.pyenv/versions/3.8.5/bin' which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.
Successfully installed pip-20.1.1 setuptools-47.1.0

}}}

----
zlibエラー時のlog

{{{
Downloading Python-3.8.5.tar.xz...
-> https://www.python.org/ftp/python/3.8.5/Python-3.8.5.tar.xz
Installing Python-3.8.5...

BUILD FAILED (Ubuntu 20.04 using python-build 1.2.20-5-g1ec3c6f1)

Inspect or clean up the working tree at /tmp/python-build.20200909091708.8543
Results logged to /tmp/python-build.20200909091708.8543.log

Last 10 log lines:
    mod_name, mod_spec, code = _get_module_details(mod_name)
  File "/tmp/python-build.20200909091708.8543/Python-3.8.5/Lib/runpy.py", line 144, in _get_module_details
    return _get_module_details(pkg_main_name, error)
  File "/tmp/python-build.20200909091708.8543/Python-3.8.5/Lib/runpy.py", line 111, in _get_module_details
    __import__(pkg_name)
  File "<frozen zipimport>", line 241, in load_module
  File "<frozen zipimport>", line 709, in _get_module_code
  File "<frozen zipimport>", line 570, in _get_data
zipimport.ZipImportError: can't decompress data; zlib not available
make: *** [Makefile:1186: install] エラー 1
}}}