Error with non-ASCII character?

[giomach]

I tried the virtual environment but the result is still the same. Here's the whole output. The highlighting is not significant.
Remember that REDACTED stands for my Windows username, which contains the character á (0xe1 in ANSI).

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

C:\Users\REDACTED>cd c:\tempenv

c:\tempenv>python -V
Python 3.9.0

c:\tempenv>pip -V
pip 20.2.3 from c:\users\redacted\appdata\local\programs\python\python39\lib\site-packages\pip (python 3.9)

c:\tempenv>python -m venv tempenv

c:\tempenv>cd tempenv

c:\tempenv\tempenv>c:\tempenv\tempenv\scripts\activate

(tempenv) c:\tempenv\tempenv>pip -V
pip 20.2.3 from c:\tempenv\tempenv\lib\site-packages\pip (python 3.9)

(tempenv) c:\tempenv\tempenv>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:\tempenv\tempenv\scripts\python.exe' 'c:\tempenv\tempenv\lib\site-packages\pip\_vendor\pep517\_in_process.py' prepare_metadata_for_build_wheel 'C:\Users\CIARND~1\AppData\Local\Temp\tmpdci12139'
         cwd: C:\Users\REDACTED\AppData\Local\Temp\pip-install-egc1g39g\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-1n7dv1ne\pyinstaller.egg-info
    writing C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\pyinstaller.egg-info\PKG-INFO
    writing dependency_links to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\pyinstaller.egg-info\dependency_links.txt
    writing entry points to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\pyinstaller.egg-info\entry_points.txt
    writing requirements to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\pyinstaller.egg-info\requires.txt
    writing top-level names to C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\pyinstaller.egg-info\top_level.txt
    writing manifest file 'C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\pyinstaller.egg-info\SOURCES.txt'
    reading manifest file 'C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\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-1n7dv1ne\pyinstaller.egg-info\SOURCES.txt'
    creating 'C:\Users\REDACTED\AppData\Local\Temp\pip-modern-metadata-1n7dv1ne\pyinstaller.dist-info'
    error: invalid command 'bdist_wheel'
    ----------------------------------------
ERROR: Command errored out with exit status 1: 'c:\tempenv\tempenv\scripts\python.exe' 'c:\tempenv\tempenv\lib\site-packages\pip\_vendor\pep517\_in_process.py' prepare_metadata_for_build_wheel 'C:\Users\CIARND~1\AppData\Local\Temp\tmpdci12139' Check the logs for full command output.
WARNING: You are using pip version 20.2.3; however, version 20.2.4 is available.
You should consider upgrading via the 'c:\tempenv\tempenv\scripts\python.exe -m pip install --upgrade pip' command.

(tempenv) c:\tempenv\tempenv>