fix flaky failure in export_integration_test.py

[tdyas]

src/python/pants/backend/python/goals/export_integration_test.py was failing for me consistently in a PR of mine and on main locally. Not sure why it passes elsewhere.

See this failure for example: https://github.com/pantsbuild/pants/actions/runs/12306576175/job/34349676205?pr=21745#step:10:478

The test is checking whether a venv activation script has a certain prompt with both a resolve name and the Python version. The test also checks whether the quote character starting that string begins with a double-quote character.

On my system for main and in the PR on CI, that quote character became a single quote instead so the test fails.

Use a regex and allow either quote character.

[tdyas]

Below is the text of the bin/activate script as seen in the test on my system.

Note the relevant part is PS1='(a/3.11.11) '"${PS1:-}".

Yet, the existing test looks for f'PS1="({resolve}/{platform.python_version()}) ' which looks for a double quote and not a single quote.

# This file must be used with "source bin/activate" *from bash*
# you cannot run it directly

deactivate () {
    # reset old environment variables
    if [ -n "${_OLD_VIRTUAL_PATH:-}" ] ; then
        PATH="${_OLD_VIRTUAL_PATH:-}"
        export PATH
        unset _OLD_VIRTUAL_PATH
    fi
    if [ -n "${_OLD_VIRTUAL_PYTHONHOME:-}" ] ; then
        PYTHONHOME="${_OLD_VIRTUAL_PYTHONHOME:-}"
        export PYTHONHOME
        unset _OLD_VIRTUAL_PYTHONHOME
    fi

    # Call hash to forget past commands. Without forgetting
    # past commands the $PATH changes we made may not be respected
    hash -r 2> /dev/null

    if [ -n "${_OLD_VIRTUAL_PS1:-}" ] ; then
        PS1="${_OLD_VIRTUAL_PS1:-}"
        export PS1
        unset _OLD_VIRTUAL_PS1
    fi

    unset VIRTUAL_ENV
    unset VIRTUAL_ENV_PROMPT
    if [ ! "${1:-}" = "nondestructive" ] ; then
    # Self destruct!
        unset -f deactivate
    fi
}

# unset irrelevant variables
deactivate nondestructive

VIRTUAL_ENV=dist/export/python/virtualenvs/a/3.11.11
export VIRTUAL_ENV

_OLD_VIRTUAL_PATH="$PATH"
PATH="$VIRTUAL_ENV/"bin":$PATH"
export PATH

# unset PYTHONHOME if set
# this will fail if PYTHONHOME is set to the empty string (which is bad anyway)
# could use `if (set -u; : $PYTHONHOME) ;` in bash
if [ -n "${PYTHONHOME:-}" ] ; then
    _OLD_VIRTUAL_PYTHONHOME="${PYTHONHOME:-}"
    unset PYTHONHOME
fi

if [ -z "${VIRTUAL_ENV_DISABLE_PROMPT:-}" ] ; then
    _OLD_VIRTUAL_PS1="${PS1:-}"
    PS1='(a/3.11.11) '"${PS1:-}"
    export PS1
    VIRTUAL_ENV_PROMPT='(a/3.11.11) '
    export VIRTUAL_ENV_PROMPT
fi

# Call hash to forget past commands. Without forgetting
# past commands the $PATH changes we made may not be respected
hash -r 2> /dev/null