The strop module and test_strop.py believe replace() with a 0 count
means "replace everything".  But the string module, string.replace()
amd test_string.py believe a 0 count means "replace nothing".
"Nothing" wins, strop loses.
Bugfix candidate.
diff --git a/Modules/stropmodule.c b/Modules/stropmodule.c
index c245794..aa9cdc7 100644
--- a/Modules/stropmodule.c
+++ b/Modules/stropmodule.c
@@ -1121,7 +1121,7 @@
 {
 	char *str, *pat,*sub,*new_s;
 	int len,pat_len,sub_len,out_len;
-	int count = 0;
+	int count = -1;
 	PyObject *new;
 
 	if (!PyArg_ParseTuple(args, "t#t#t#|i:replace",