A very strange understanding of the concept of immutable.

I have same problem.
"Checkmate (often shortened to mate) is any game position in chess and other chess-like games in which a player's king is in check (threatened with capture) and there is no possible escape."
Where's the catch?

There no needs of itertools. I have forgot to delete this line.

All tests are passed except this one. Where is the problem?

Random test with message: ZEbzB hqUDgDQxx izNy c QNrcDFcmFFibWWGPRjBk n
... and rows: 4
ReferenceError: chunk is not defined
at encode
at /home/codewarrior/index.js:165:31
at begin
at it
at /home/codewarrior/index.js:146:3
at /runner/frameworks/javascript/cw-2.js:152:11
at Promise._execute
at Promise._resolveFromExecutor
at new Promise
at describe
at /home/codewarrior/index.js:135:1
at /home/codewarrior/index.js:176:5
at Object.handleError