Returns a list of names of available virtual environments.

        :raises: DjangoDevException on errors
        :rtype: list
        :return: list of names

def get_venvs(self):
        """Returns a list of names of available virtual environments.

        :raises: DjangoDevException on errors
        :rtype: list
        :return: list of names
        """

        def raise_():
            error_str = 'Virtual environments are not created. Please run `bootstrap` command.'
            self.logger.error(error_str)
            raise DjangoDevException(error_str)

        if not os.path.exists(self.venvs_path):
            raise_()
        venvs = os.listdir(self.venvs_path)
        if not venvs:
            raise_()

        venvs.sort()
        return venvs