tests/thread: Improve modthread.c test coverage.

tests/thread/thread_exc2.py

@@ -0,0 +1,10 @@
+# test raising exception within thread which is not caught
+import utime
+import _thread
+
+def thread_entry():
+    raise ValueError
+
+_thread.start_new_thread(thread_entry, ())
+utime.sleep(1)
+print('done')