Spurt out more descriptive error messages in an unlikely event of url…

….join failing

src/matrix/mod.rs

@@ -105,7 +105,8 @@ impl MatrixClient {
 
  pub fn send_text_message(&mut self, room_id: &str, body: String) -> impl Future<Item=protocol::RoomSendResponse, Error=io::Error> {
  let msg_id = thread_rng().gen::<u16>();
- let mut url = self.url.join(&format!("/_matrix/client/r0/rooms/{}/send/m.room.message/mircd-{}", room_id, msg_id)).unwrap();
+ let mut url = self.url.join(&format!("/_matrix/client/r0/rooms/{}/send/m.room.message/mircd-{}", room_id, msg_id))
+ .unwrap("Unable to construct a valid API url");
  url.query_pairs_mut()
  .clear()
  .append_pair("access_token", &self.access_token);
@@ -119,7 +120,8 @@ impl MatrixClient {
 
  pub fn join_room(&mut self, room_id: &str) -> impl Future<Item=protocol::RoomJoinResponse, Error=io::Error> {
  let roomid_encoded = percent_encode(room_id.as_bytes(), PATH_SEGMENT_ENCODE_SET);
- let mut url = self.url.join(&format!("/_matrix/client/r0/join/{}", roomid_encoded)).unwrap();
+ let mut url = self.url.join(&format!("/_matrix/client/r0/join/{}", roomid_encoded))
+ .unwrap("Unable to construct a valid API url");
  url.query_pairs_mut()
  .clear()
  .append_pair("access_token", &self.access_token);