def install_pip(self, package, save=True, save_dev=False):
        """Installs a pip package.

        :param save: if `True`, pins the package to the Hydrogen requirements
            YAML file.
        :param save_dev: if `True`, pins the package as a development
            dependency to the Hydrogen requirements YAML file.
        :param return: a **single** :class:`Requirement` object, representing
            the installed version of the given package.
        """
        requirement = Requirement.coerce(package)
        click.echo("pip install " + requirement.package)
        cmd = envoy.run("pip install {}".format(str(requirement)))
        if cmd.status_code == 0:
            installed_packages = get_installed_pypackages()
            package = installed_packages[requirement.package]
            requirement.version = "=={}".format(package.version)
            if save:
                self.requirements["all"].add(requirement)
            if save_dev:
                self.requirements["dev"].add(requirement)
            if save or save_dev:
                self.requirements.save()
            return requirement
        else:
            fatal(cmd.std_err)
def visitdir(self, path):
        """Similar to matcher.visitdir"""
        path = normalizerootdir(path, "visitdir")
        if self.matchrecursive:
            return "all"
        elif self.unsurerecursive:
            return True
        elif path == "":
            return True

        if self._kindpats and self._compiledpats(path):
            # XXX: This is incorrect. But re patterns are already used in
            # production. We should kill them!
            # Need to test "if every string starting with 'path' matches".
            # Obviously it's impossible to test *every* string with the
            # standard regex API, therefore pick a random strange path to test
            # it approximately.
            if self._compiledpats("%s/*/_/-/0/*" % path):
                return "all"
            else:
                return True

        if self._globdirpats and self._compileddirpats(path):
            return True

        subdir, rest = self._split(path)
        subtree = self.get(subdir)
        if subtree is None:
            return False
        else:
            return subtree.visitdir(rest)