Add msisdn util file

synapse/util/msisdn.py

+# -*- coding: utf-8 -*-
+# Copyright 2015, 2016 OpenMarket Ltd
+# Copyright 2017 Vector Creations Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import phonenumbers
+from synapse.api.errors import SynapseError
+
+def phone_number_to_msisdn(country, number):
+    try:
+        phoneNumber = phonenumbers.parse(number, country)
+    except phonenumbers.NumberParseException:
+        raise SynapseError(400, "Unable to parse phone number")
+    return phonenumbers.format_number(
+        phoneNumber, phonenumbers.PhoneNumberFormat.E164
+    )[1:]