Run a pip command.

    Args:
        command_args (list of str): Args to pip.

    Returns:
        `subprocess.Popen`: Pip process.

def run_pip_command(command_args, pip_version=None, python_version=None):
    """Run a pip command.

    Args:
        command_args (list of str): Args to pip.

    Returns:
        `subprocess.Popen`: Pip process.
    """
    pip_exe, context = find_pip(pip_version, python_version)
    command = [pip_exe] + list(command_args)

    if context is None:
        return popen(command)
    else:
        return context.execute_shell(command=command, block=False)