Added unban command.

commands/unban.js

+const errors = require('../errors.json');
+
+exports.run = async (client, message, args) => {
+    if (!message.member.hasPermission('BAN_MEMBERS')) {
+        message.channel.send(errors.insufficient_permission_for_user).catch(e => {
+            return;
+        });
+        return;
+    };
+
+    function GetUser(user) {
+        if (user.length == 18) {
+            return user;
+        } else if (user.length == 22) {
+            return user.slice(3, 21);
+        } else if (user.length == 21) {
+            return user.slice(3, 20);
+        } else {
+            return user;
+        };
+    };
+
+    const user = args[0]
+    if (!user) {
+        message.channel.send(errors.insufficient_args).catch(e => {
+            return;
+        });
+        return;
+    };
+
+    let reason = args.slice(1).join(' ');
+    if (!reason) {
+        reason = "Unspecified."
+    }
+
+    message.guild.fetchBans().then(bans => {
+        if(bans.size == 0) {
+            message.channel.send('There is no ban on this guild.').catch(e => {
+                return;
+            });
+            return;
+        };
+        const ban = bans.find(b => b.user.id == GetUser(user));
+        if (!ban) {
+            message.channel.send('Cannot find that user or that user is not banned.').catch(e => {
+                return;
+            });
+            return
+        };
+        message.guild.members.unban(ban.user).catch(e => {
+            message.channel.send(errors.insufficient_permission_for_bot).catch(e => {
+                return;
+            });
+            return;
+        });
+        message.channel.send('Successfully performed unban on specified user.').catch(e => {
+            return;
+        });
+    });
+};
+
+module.exports.help = {
+    name: 'unban',
+    aliases: []
+};
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