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 __init__(self, root, cwd, kindpats, ctx=None, badfn=None):
        super(patternmatcher, self).__init__(root, cwd, badfn)
        # kindpats are already normalized to be relative to repo-root.
        # Can we use tree matcher?
        rules = _kindpatstoglobs(kindpats, recursive=False)
        fallback = True
        if rules is not None:
            try:
                matcher = treematcher(root, cwd, badfn=badfn, rules=rules)
                # Replace self to 'matcher'.
                self.__dict__ = matcher.__dict__
                self.__class__ = matcher.__class__
                fallback = False
            except ValueError:
                # for example, Regex("Compiled regex exceeds size limit of 10485760 bytes.")
                pass
        if fallback:
            self._prefix = _prefix(kindpats)
            self._pats, self.matchfn = _buildmatch(ctx, kindpats, "$", root)

        self._files = _explicitfiles(kindpats)