Ensure log file encoding is utf-8

[itsayellow]

• I have added an entry to docs/changelog.md

Summary of changes

Makes sure that utf-8 encoding is used for log files, to prevent UnicodeEncodeErrors from occurring with emoji.

This was a problem on Windows with Python < 3.9.

Closes #645

Test plan

Tested by running

pipx install -e pycowsay

This PR in Windows Powershell Python3.7:

> pipx install -e pycowsay
⚠️  Ignoring --editable install option. pipx disallows it for anything but a local path, to avoid having to create a
    new src/ directory.
  installed package pycowsay 0.0.0.1, Python 3.7.9
  These apps are now globally available
    - pycowsay.exe
done! ✨ 🌟 ✨

pipx 0.16.1.0 in Windows Powershell Python 3.7

> pipx install -e pycowsay
    new src/ directory.
--- Logging error ---
Traceback (most recent call last):
  File "C:\Program Files\Python37\lib\logging\__init__.py", line 1028, in emit
    stream.write(msg + self.terminator)
  File "C:\Program Files\Python37\lib\encodings\cp1252.py", line 19, in encode
    return codecs.charmap_encode(input,self.errors,encoding_table)[0]
UnicodeEncodeError: 'charmap' codec can't encode characters in position 46-47: character maps to <undefined>
Call stack:
  File "C:\Users\mclapp\git\pipx\venv3.7\Scripts\pipx-script.py", line 33, in <module>
    sys.exit(load_entry_point('pipx', 'console_scripts', 'pipx')())
  File "c:\users\mclapp\git\pipx\src\pipx\main.py", line 759, in cli
    return run_pipx_command(parsed_pipx_args)
  File "c:\users\mclapp\git\pipx\src\pipx\main.py", line 202, in run_pipx_command
    suffix=args.suffix,
  File "c:\users\mclapp\git\pipx\src\pipx\commands\install.py", line 67, in install
    suffix=suffix,
  File "c:\users\mclapp\git\pipx\src\pipx\venv.py", line 224, in install_package
    package_or_url, pip_args
  File "c:\users\mclapp\git\pipx\src\pipx\package_specifier.py", line 154, in parse_specifier_for_install
    subsequent_indent=" " * 4,
Message: '⚠️  Ignoring --editable install option. pipx disallows it for anything but a local path, to avoid having to create a\n    new src/ directory.'
Arguments: ()
  installed package pycowsay 0.0.0.1, Python 3.7.9
  These apps are now globally available
    - pycowsay.exe
done! ✨ 🌟 ✨

[uranusjr]

I wonder if this could cause crashes if there’s an existing log file written in platform encoding.

[itsayellow]

I wonder if this could cause crashes if there’s an existing log file written in platform encoding.

I don't think this is a problem because we start a new log file for each command. So we're not appending to an existing file.

[itsayellow]

I just did a quick test and things seem to work ok even with append and different encodings:

> python3
Python 3.9.2 (default, Feb 24 2021, 13:26:09) 
[Clang 12.0.0 (clang-1200.0.32.29)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> with open("test.txt","w",encoding="ascii") as test_fh:
...   print("hi", file=test_fh)
... 
>>> with open("test.txt","a",encoding="utf-8") as test_fh:
...   print("hi🙂", file=test_fh)
... 
>>> exit()
birchtree:pipx file test.txt
test.txt: UTF-8 Unicode text
> more test.txt
hi
hi🙂