message: oauth2.rs: Fix get_access_token
  Comment suggests that if the token is expired, fetch another one,
  this commits fixes the code in accordance with the comment
diff: @@ -139,15 +139,19 @@ impl SpotifyClientCredentials {
  /// get access token from self.token_info, if self.token_info is none or is
  /// expired. fetch token info by HTTP request
  pub fn get_access_token(&self) -> String {
  - let mut access_token = String::new();
  - match self.token_info {
  + let access_token = match self.token_info {
  Some(ref token_info) => {
  if !self.is_token_expired(token_info) {
  debug!("token info: {:?}", &token_info);
  - access_token = token_info.access_token.to_owned();
  + Some(&token_info.access_token)
  + } else {
  + None
  }
  - access_token
  }
  + None => None
  + };
  + match access_token {
  + Some(access_token) => access_token.to_owned(),
  None => {
  match self.request_access_token() {
  Some(new_token_info) => {
  