Returns a private key (adding header & footer if required).

        :param key A private key
        :type: string

        :param heads: True if we want to include head and footer
        :type: boolean

        :returns: Formated private key
        :rtype: string

def format_private_key(key, heads=True):
        """
        Returns a private key (adding header & footer if required).

        :param key A private key
        :type: string

        :param heads: True if we want to include head and footer
        :type: boolean

        :returns: Formated private key
        :rtype: string
        """
        private_key = key.replace('\x0D', '')
        private_key = private_key.replace('\r', '')
        private_key = private_key.replace('\n', '')
        if len(private_key) > 0:
            if private_key.find('-----BEGIN PRIVATE KEY-----') != -1:
                private_key = private_key.replace('-----BEGIN PRIVATE KEY-----', '')
                private_key = private_key.replace('-----END PRIVATE KEY-----', '')
                private_key = private_key.replace(' ', '')
                if heads:
                    private_key = "-----BEGIN PRIVATE KEY-----\n" + "\n".join(wrap(private_key, 64)) + "\n-----END PRIVATE KEY-----\n"
            else:
                private_key = private_key.replace('-----BEGIN RSA PRIVATE KEY-----', '')
                private_key = private_key.replace('-----END RSA PRIVATE KEY-----', '')
                private_key = private_key.replace(' ', '')
                if heads:
                    private_key = "-----BEGIN RSA PRIVATE KEY-----\n" + "\n".join(wrap(private_key, 64)) + "\n-----END RSA PRIVATE KEY-----\n"
        return private_key