Odd permission error when installing Plone 5.2 on Debian 10 (Buster)

This is an installation of Plone 5.2 on a stock (fresh install) of Debian 10 (Buster). During the installation (standalone with Python 3 (although the same result with Python 2) with default options (/opt/plone, etc.). Note the permission problem with /root/.cache (even though I was logged in as a regular (sudo-able) user rather than root. Moreover, python-pip and python3-pip were both installed on the OS.


~/Downloads/Plone-5.2.0-UnifiedInstaller-r1$ sudo -H ./install.sh

ls: cannot access '/opt/plone/Python-*/bin/python[23]': No such file or directory
Testing /usr/bin/python3.7 for Zope/Plone requirements....
/usr/bin/python3.7 looks OK. We will use it.

Root install method chosen. Will install for use by users:
ZEO & Client Daemons: plone_daemon
Code Resources & buildout: plone_buildout

Detailed installation log being written to /home/ronc/Downloads/Plone-5.2.0-UnifiedInstaller-r1/install.log
Installing Plone 5.2.0 at /opt/plone

Using useradd and groupadd to create users and groups.
plone_group already exists; no need to create it.
User plone_daemon already exists. No need to create it.
Adding user plone_daemon to group plone_group.
User plone_buildout already exists. No need to create it.
Adding user plone_buildout to group plone_group.
Creating Python virtual environment.
Using base prefix '/usr'
New python executable in /opt/plone/zinstance/bin/python3.7
Also creating executable in /opt/plone/zinstance/bin/python
Installing setuptools, pip, wheel...

Complete output from command /opt/plone/zinstance/bin/python3.7 - setuptools pip wheel:
WARNING: The directory '/root/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
WARNING: The directory '/root/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Looking in links: /home/ronc/Downloads/Plone-5.2.0-UnifiedInstaller-r1/packages/virtualenv-16.6.0/virtualenv_support
Collecting setuptools
ERROR: Could not install packages due to an EnvironmentError: [Errno 13] Permission denied: '/root/.cache/pip/wheels/11/81/99/6a33f06c433befbe8f202a7b4c2a197fa89d76db9d7e9f7932'
Consider using the --user option or check the permissions.


...Installing setuptools, pip, wheel...done.
Installing Python requirements in virtual environment.
Unable to install Python requirements in virtual environment.

Installation has failed.
See the detailed installation log at /home/ronc/Downloads/Plone-5.2.0-UnifiedInstaller-r1/install.log
to determine the cause.

Here are the contents of the install.log file:

Detailed installation log
Starting at Mon 05 Aug 2019 08:50:02 PM CDT
Traceback (most recent call last):
File "virtualenv.py", line 2580, in
main()
File "virtualenv.py", line 831, in main
symlink=options.symlink,
File "virtualenv.py", line 1123, in create_environment
install_wheel(to_install, py_executable, search_dirs, download=download)
File "virtualenv.py", line 973, in install_wheel
_install_wheel_with_search_dir(download, project_names, py_executable, search_dirs)
File "virtualenv.py", line 1060, in _install_wheel_with_search_dir
call_subprocess(cmd, show_stdout=False, extra_env=env, stdin=script)
File "virtualenv.py", line 924, in call_subprocess
raise OSError("Command {} failed with error code {}".format(cmd_desc, proc.returncode))
OSError: Command /opt/plone/zinstance/bin/python3.7 - setuptools pip wheel failed with error code 1
sudo: /opt/plone/zinstance/bin/pip: command not found

It looks like there's a related issue ticket: https://github.com/plone/Installers-UnifiedInstaller/issues/84

I'd missed that earlier, but will now tackle it.

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