capybara/virtualenv/lib/python2.7/site-packages/pip/req/req_set.py
def _walk_req_to_install(self, handler):
        """Call handler for all pending reqs.

        :param handler: Handle a single requirement. Should take a requirement
            to install. Can optionally return an iterable of additional
            InstallRequirements to cover.
        """
        # The list() here is to avoid potential mutate-while-iterating bugs.
        discovered_reqs = []
        reqs = itertools.chain(
            list(self.unnamed_requirements), list(self.requirements.values()),
            discovered_reqs)
        for req_to_install in reqs:
            more_reqs = handler(req_to_install)
            if more_reqs:
                discovered_reqs.extend(more_reqs)
def _walk_req_to_install(self, handler):
        """Call handler for all pending reqs.

        :param handler: Handle a single requirement. Should take a requirement
            to install. Can optionally return an iterable of additional
            InstallRequirements to cover.
        """
        # The list() here is to avoid potential mutate-while-iterating bugs.
        discovered_reqs = []
        reqs = itertools.chain(
            list(self.unnamed_requirements), list(self.requirements.values()),
            discovered_reqs)
        for req_to_install in reqs:
            more_reqs = handler(req_to_install)
            if more_reqs:
                discovered_reqs.extend(more_reqs)
Call handler for all pending reqs.

        :param handler: Handle a single requirement. Should take a requirement
            to install. Can optionally return an iterable of additional
            InstallRequirements to cover.