nlr: Add even more optional debugging logging.

Has to be enabled by manual editing, but at least it's there, as debugging
NLR issues may be weird.

py/nlr.h

@@ -91,6 +91,8 @@ void nlr_jump_fail(void *val);
 #include "mpstate.h"
 #define nlr_raise(val) \
     do { \
+        /*printf("nlr_raise: nlr_top=%p\n", MP_STATE_VM(nlr_top)); \
+        fflush(stdout);*/ \
         void *_val = val; \
         assert(_val != NULL); \
         assert(mp_obj_is_exception_instance(_val)); \
@@ -100,6 +102,12 @@ void nlr_jump_fail(void *val);
 #define nlr_push(val) \
     assert(MP_STATE_VM(nlr_top) != val),nlr_push(val)
 
+/*
+#define nlr_push(val) \
+    printf("nlr_push: before: nlr_top=%p, val=%p\n", MP_STATE_VM(nlr_top), val),assert(MP_STATE_VM(nlr_top) != val),nlr_push(val)
+#endif
+*/
+
 #endif
 
 #endif // __MICROPY_INCLUDED_PY_NLR_H__