     public var description: String {
         switch self {
         case .noGithubToken:
-            return "[SpeakerError] Lack of GitHub token."
+            return "[\(type(of: self))] Lack of GitHub token."
         case .noOutputDirectoryPath:
-            return "[SpeakerError] Lack of image output directory path."
+            return "[\(type(of: self))] Lack of image output directory path."
         case .noTwitterCredential:
-            return "[SpeakerError] Lack of Twitter credential."
+            return "[\(type(of: self))] Lack of Twitter credential."
         }
     }
 }


extension APIError : CustomStringConvertible {
    public var description: String {
        return "[APIError] response = \(response), json = \(json)"
    }
}


    public var description: String {
        switch self {
        case .illegalResponse:
            return "[\(type(of: self))] Illegal response during code rendering."
        case .writingFailed:
            return "[\(type(of: self))] Failed to write images of code."
        }
    }
}
