Error with non-ASCII character?

[snippsat]

Error:
SyntaxError: (unicode error) 'utf-8' codec can't decode byte 0xe1 in position 0: unexpected end of data (sitecustomize.py, line 7)

Have you made this sitecustomize.py yourself)
It's not a part of original file as least in Python 3.8,has not 3.9 yet.
This is a file i have made myself in the past look at this post.

Dos other pip install works?

pip install requests

Can try to run a virtual environment(build into Python),this is was i always do if help someone with Pyinstaller,to get all new installation.
A demo i use cmder(recommend),commnad is just the same in cmd.

# Test python
E:\div_code
λ python -V
Python 3.8.3

# Test pip
E:\div_code
λ pip -V
pip 20.2.3 from c:\python38\lib\site-packages\pip (python 3.8)

# Make environment  
E:\div_code
λ python -m venv my_env

# cd in
E:\div_code
λ cd my_env\

# Activate, see (my_env) 
E:\div_code\my_env
λ E:\div_code\my_env\Scripts\activate

# Test pip again,now point to this folder
(my_env) E:\div_code\my_env
λ pip -V
pip 19.2.3 from e:\div_code\my_env\lib\site-packages\pip (python 3.8)

# Install
(my_env) E:\div_code\my_env
λ pip install pyinstaller
Collecting pyinstaller
  Downloading ..... 
Successfully installed altgraph-0.17 future-0.18.2 pefile-2019.4.18 pyinstaller-4.0 pyinstaller-hooks-contrib-2020.10 pywin32-ctypes-0.2.0

# Move python file this folder and run Pyinstaller
(my_env) E:\div_code\my_env