Temporary solution for crashing when using both :py and :py3: disallow both in
one session.
diff --git a/src/proto/if_python3.pro b/src/proto/if_python3.pro
index f9921e1..9c132c3 100644
--- a/src/proto/if_python3.pro
+++ b/src/proto/if_python3.pro
@@ -1,6 +1,7 @@
/* if_python3.c */
int python3_enabled __ARGS((int verbose));
void python3_end __ARGS((void));
+int python3_loaded __ARGS((void));
void ex_py3 __ARGS((exarg_T *eap));
void ex_py3file __ARGS((exarg_T *eap));
void python3_buffer_free __ARGS((buf_T *buf));