def update_virtualenv():
    """Updates virtual Python environment."""
    ve_dir = cget("virtualenv_dir")
    activate = pjoin(ve_dir, "bin", "activate")
    cache = cget("pip_cache")

    show(yellow("Updating Python virtual environment."))
    show(green("Be patient. It may take a while."))

    for req in cget('pip_requirements'):
        requirements = pjoin(remote_files_dir('requirements'), req)
        show(yellow("Processing requirements file: %s" % requirements))
        with settings(warn_only=True):
            with prefix(activate % "source %s"):
                run("pip install --no-input --download-cache=%s"
                    " --requirement %s --log=/tmp/pip.log" %
                    (cache, requirements))
dataset/ETHPy150Open ipeirotis/Mturk-Tracker/deployment/modules/virtualenv.py/update_virtualenv/swapped operands of `%`