clojure.test output I've observed without the patch:

ERROR in (chown-test) (core.clj:4409)
expected: (= nil (observe-act p true))
  actual: clojure.lang.ExceptionInfo: No such group "nobody"
 at clojure.core$ex_info.invoke (core.clj:4409)
    [...]

With 0002-CLJ-1209-show-ex-data-in-clojure-test.patch:

ERROR in (chown-test) (core.clj:4409)
expected: (= nil (observe-act p true))
  actual: clojure.lang.ExceptionInfo: No such group "nobody"
{:group "nobody", :path #<UnixPath /tmp/chown-test479458711256463218file>}
 at clojure.core$ex_info.invoke (core.clj:4409)
    [...]