When windows users use "python -m venv ENV_DIR", a python virtual environment will be created in ENV_DIR. 
Powershell users use ENV_DIR\Scripts\Activate.ps1 to activate virtual environment.
In powershell, a environment variable, "$env:VIRTUAL_ENV", is set and used by many tools to determine that there is an activated venv. In bash, it is "$VIRTUAL_ENV"
In python3.8 and python3.9, $env:VIRTUAL_ENV has a redundant '/', for example:
PS C:\Users\Test> python -m venv test_venv
PS C:\Users\Test> .\test_venv\Scripts\Activate.ps1
PS C:\Users\Test> $env:VIRTUAL_ENV
C:\Users\Test\test_venv/

using python3.7, or using virtualenv with python3.8 or 3.9, or in linux, there will be no such a '/' in the end.

This '/' matters because some tools many tools use this environment variable, for example, oh-my-posh will take "test_venv/" as virtual environment name rather than "test_venv"(Although venv's activate.ps 1 itself's default prompt is correct). And from the perspective of semantics and consistency with other platform, the '/' is redundant.

New changeset 787b6d548c250f36df6d3f3179f60d754c8aa5e3 by schwarzichet in branch 'master':
bpo-39505: delete the redundant '/' in $env:VIRTUAL_ENV (GH-18290)
https://github.com/python/cpython/commit/787b6d548c250f36df6d3f3179f60d754c8aa5e3

New changeset 927d3aab1c7874b5705fcc8269ea608315434e66 by Miss Islington (bot) in branch '3.8':
bpo-39505: delete the redundant '/' in $env:VIRTUAL_ENV (GH-18290) (GH-18359)
https://github.com/python/cpython/commit/927d3aab1c7874b5705fcc8269ea608315434e66