process hanging in embeded mode on exception

As a FUP of #221 which provided a new pathway to see the exception,
but does not prevent the "hanging" in an other pathway.

The simplest scenario is that we have a hanging python process by using this clojure code crash.clj

(ns train
  (:require [libpython-clj2.python :refer [py.- py.] :as py]
            [libpython-clj2.python.ffi :as ffi]))

(def locked (ffi/lock-gil))
(py/import-module "not existing")

and load it in embedded mode using manual-gil via:

export JDK_JAVA_OPTIONS="-Dlibpython_clj.manual_gil=true"
python -c 'from clojurebridge import cljbridge;cljbridge.load_clojure_file(clj_file="crash.clj")'

The exception thrown by python on the last line in crash.clj is swallowed by either clojurebridge or libpython-clj and the process hangs forever.

まず、manual-gil 下で crash.clj、ffi/lock-gil、py/import-module、clojurebridge.load_clojure_file を使ってハングを再現します。見つからないモジュールからの例外が clojurebridge と libpython-clj の間でどのように処理されるかを追跡します。埋め込みプロセスがハングせずに終了または戻り、例外が表示されたままになれば完了です。