Error with non-ASCII character?

[giomach]

Python reinstalled to C:\Program Files\Python39 (which is where I want it anyway), everything done as administrator, installed for all users, added to PATH. But same error again in installing pyinstaller. REDACTED below replaces my Windows username, which contains the character á (0xe1 in ANSI), which is being misinterpreted as being in utf8 instead of ANSI, whence error. Please ignore highlighting. There is no sitecustomize.py in my file system.

Microsoft Windows [Version 10.0.19041.572]
(c) 2020 Microsoft Corporation. All rights reserved.

C:\WINDOWS\system32>python
Python 3.9.0 (tags/v3.9.0:9cf6752, Oct  5 2020, 15:34:40) [MSC v.1927 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()

C:\WINDOWS\system32>python -V
Python 3.9.0

C:\WINDOWS\system32>py -m pip install --upgrade pip
Requirement already up-to-date: pip in c:\program files\python39\lib\site-packages (20.2.4)

C:\WINDOWS\system32>py -m pip install pyinstaller
Collecting pyinstaller
  Using cached pyinstaller-4.0.tar.gz (3.5 MB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... done
    Preparing wheel metadata ... error
    ERROR: Command errored out with exit status 1:
     command: 'C:\Program Files\Python39\python.exe' 'C:\Program Files\Python39\lib\site-packages\pip\_vendor\pep517\_in_process.py' prepare_metadata_for_build_wheel 'C:\Users\CIARND~1\AppData\Local\Temp\tmpm0upp60n'
         cwd: C:\Users\REDACTED\AppData\Local\Temp\pip-install-jw1e9dw4\pyinstaller
    Complete output (38 lines):
    Error in sitecustomize; set PYTHONVERBOSE for traceback:
    SyntaxError: (unicode error) 'utf-8' codec can't decode byte 0xe1 in position 0: unexpected end of data (sitecustomize.py, line 21)
    running dist_info
    creating C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info
    writing C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\PKG-INFO
    writing dependency_links to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\dependency_links.txt
    writing entry points to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\entry_points.txt
    writing requirements to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\requires.txt
    writing top-level names to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\top_level.txt
    writing manifest file 'C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\SOURCES.txt'
    reading manifest file 'C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\SOURCES.txt'
    reading manifest template 'MANIFEST.in'
    warning: no files found matching 'pyinstaller-gui.py'
    no previously-included directories found matching 'bootloader\build'
    no previously-included directories found matching 'bootloader\.waf-*'
    no previously-included directories found matching 'bootloader\.waf3-*'
    no previously-included directories found matching 'bootloader\waf-*'
    no previously-included directories found matching 'bootloader\waf3-*'
    no previously-included directories found matching 'bootloader\_sdks'
    no previously-included directories found matching 'bootloader\.vagrant'
    warning: no previously-included files found matching 'bootloader\.lock-waf*'
    no previously-included directories found matching 'doc\source'
    no previously-included directories found matching 'doc\_build'
    warning: no previously-included files matching '*.tmp' found under directory 'doc'
    warning: no files found matching 'news\_template.rst'
    no previously-included directories found matching 'news'
    no previously-included directories found matching 'old'
    no previously-included directories found matching 'scripts'
    no previously-included directories found matching 'tests\scripts'
    no previously-included directories found matching '.github'
    warning: no previously-included files found matching '.*'
    warning: no previously-included files found matching '*.yml'
    warning: no previously-included files found matching '*~'
    warning: no previously-included files found matching '.directory'
    warning: no previously-included files matching '*.py[co]' found anywhere in distribution
    writing manifest file 'C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.egg-info\SOURCES.txt'
    creating 'C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-48slrgbm\pyinstaller.dist-info'
    error: invalid command 'bdist_wheel'
    ----------------------------------------
ERROR: Command errored out with exit status 1: 'C:\Program Files\Python39\python.exe' 'C:\Program Files\Python39\lib\site-packages\pip\_vendor\pep517\_in_process.py' prepare_metadata_for_build_wheel 'C:\Users\CIARND~1\AppData\Local\Temp\tmpm0upp60n' Check the logs for full command output.

C:\WINDOWS\system32>
C:\WINDOWS\system32>

I think it's time to file a bug report. How do I do that?