Error printing return value of try monad in REPL

Using cats in CIDER + nREPL yields:

```
;; CIDER 0.22.0snapshot (package: 20190326.1752), nREPL 0.6.0
;; Clojure 1.10.0, Java 1.8.0_201

user> (require '[cats.monad.exception :as exc])
(exc/try-on 1)
nilError printing return value (IllegalArgumentException) at clojure.lang.MultiFn/findAndCacheBestMethod (MultiFn.java:179).
Multiple methods in multimethod 'simple-dispatch' match dispatch value: class cats.monad.exception.Success -> interface clojure.lang.IDeref and interface clojure.lang.IPersistentMap, and neither is preferred
```