`Error: Not supported` when trying to connect with wrong username

[jonasfrey]

i have the following users setup in my mysql db

select * from mysql.user;

+-----------+------------------
| Host      | User             
+-----------+------------------
| localhost | debian-sys-maint 
| localhost | mysql.infoschema 
| localhost | mysql.session    
| localhost | mysql.sys        
| localhost | root             
+-----------+------------------

when i now try to connect with a wrong non-existing user i get no error at all

const client = await new Client().connect({
  hostname: "127.0.0.1",
  username: "testuser",
  password: "Test12342",
});

when i then try to execute a sql query i get the following uninformative error message:

await client.execute(`CREATE DATABASE IF NOT EXISTS enok`);

error: Uncaught (in promise) Error: Not supported
      throw new Error("Not supported");
            ^
    at auth (https://deno.land/x/mysql@v2.11.0/src/auth.ts:41:13)
    at PoolConnection._connect (https://deno.land/x/mysql@v2.11.0/src/connection.ts:118:24)
    at async PoolConnection.connect (https://deno.land/x/mysql@v2.11.0/src/connection.ts:179:5)
    at async Client.createConnection (https://deno.land/x/mysql@v2.11.0/src/client.ts:47:5)
    at async DeferredStack.creator (https://deno.land/x/mysql@v2.11.0/src/pool.ts:67:20)
    at async DeferredStack.pop (https://deno.land/x/mysql@v2.11.0/src/deferred.ts:35:16)
    at async ConnectionPool.pop (https://deno.land/x/mysql@v2.11.0/src/pool.ts:99:14)
    at async Client.useConnection (https://deno.land/x/mysql@v2.11.0/src/client.ts:105:24)
    at async Client.execute (https://deno.land/x/mysql@v2.11.0/src/client.ts:96:12)

i would expect the following message

error: Uncaught (in promise) Error: Access denied for user 'testuser'@'localhost' (using password: YES)

i found out that this happens only for the strings 'testuser*' and 'root*', so for example username 'a_root' would give the correct error, or username 'a_testuser'