From the error I think the quotes are not properly escaped while doing text replacement in venv activate file template at [0] while it's generated? On linux/Mac double quotes are used and hence the error is not triggered with single quote in virtualenv name. Using double quote in virtualenv name triggers the parse error.

$  python3.7 -m venv py37\"-bpo-35667-venv
$  source py37\"-bpo-35667-venv/bin/activate
py37"-bpo-35667-venv/bin/activate:57: parse error near `then'

Looking into the py37\"-bpo-35667-venv/bin/activate script there is below line where the double quote is unbalanced : 

    if [ "x(py37"-bpo-35667-venv) " != x ] ; then
	PS1="(py37"-bpo-35667-venv) ${PS1:-}"
    else

I tried escaping the quotes with backslash at [0] but I get a similar error. I guess it's similar case in Powershell as I can see from Activate.ps1 but I haven't tested it. I am not sure about the difference in semantics between powershell and command prompt with respect to quoting since I don't have access to Windows.

py37\'-bpo-35667-venv/bin/Activate.ps1 file with unbalanced quote

    function global:prompt {
        Write-Host -NoNewline -ForegroundColor Green '(py37'-bpo-35667-venv) '
        _OLD_VIRTUAL_PROMPT
    }


[0] https://github.com/python/cpython/blob/a5b76167dedf4d15211a216c3ca7b98e3cec33b8/Lib/venv/__init__.py#L280