gistfile1.md

clojure.lang.ExceptionInfo: Request: [{:body {:foo "bar"}, :query-string nil, :uri "/users"}]<BR>==> Error: [{:foo disallowed-key, :username missing-required-key}]<BR>==> Context: [:body]
    data: {:type :coercion-error,
           :schema {:username java.lang.String},
           :data {:foo "bar"},
           :context :body}

Try destructuring it with slingshot:

(try+ (handler request)
          (catch [:type :coercion-error] {:keys [schema data]
                                          :as e} 
            (warn e)
            (invalid-request data))