capybara/virtualenv/lib/python2.7/site-packages/pip/baseparser.py
def get_environ_vars(self):
        """Returns a generator with all environmental vars with prefix PIP_"""
        for key, val in os.environ.items():
            if _environ_prefix_re.search(key):
                yield (_environ_prefix_re.sub("", key).lower(), val)
def get_environ_vars(self):
        """Returns a generator with all environmental vars with prefix PIP_"""
        for key, val in os.environ.items():
            if _environ_prefix_re.search(key):
                yield (_environ_prefix_re.sub("", key).lower(), val)
Returns a generator with all environmental vars with prefix PIP_