Rust is very well optimized for developer happiness. Built in decent package manager, minor type system annoyances that do not cause real slow down once you get the hang of it.
If you say Java is optimized for developer happiness, or worse, Haskell, I'll pass on this cheap trolling attempt.
C family is not optimized for happiness at all, not with the hours spent debugging someone else's bugs that break your code.
C# is somewhat better Java. Still not good enough.
Python and Ruby are, but you'll curse the day you have to performance optimize code. Object Pascal and Visual Basic, but they're rarely used for systems programming nowadays.
Perl has not shaken the write only language moniker, even with Perl 6.
What are your other suggestions? Smalltalk or Squeak? Lisp? I think the people have spoken on these...
JavaScript with all the silent bugs you can make in it, and the awkwardness of the runtime?