You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: errors.rs
    path of file: ./repos/sudo_pair/sudo_pair/src
    
    the code of the file until where you have to start completion: // Copyright 2018 Square Inc.
//
// 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" BASI
    
    fn as_str(&self) -> &'static str {
        match self {
            ErrorKind::CommunicationError => "couldn't establish communications with the pair",
            ErrorKind::SessionDeclined    => "pair declined the session",
            ErrorKind::SessionTerminated  => "pair ended the session",
            ErrorKind::StdinRedirected    => "redirection of stdin to paired sessions is prohibited",
            ErrorKind::SudoToUserAndGroup => "the -u and -g options may not both be specified",

            ErrorKind::PluginError(_)     => "the plugin failed to initialize",
        }
    }