sparse: raise a move verbose index error from the C code

sparse: raise a move verbose index error from the C code

If we don't like a value we should print it.

--- a/mercurial/cext/revlog.c	Fri Oct 05 23:10:56 2018 +0300
+++ b/mercurial/cext/revlog.c	Tue Nov 27 02:10:14 2018 +0100
@@ -1189,7 +1189,8 @@
 			goto bail;
 		}
 		if (revnum < 0 || revnum >= idxlen) {
-			PyErr_SetString(PyExc_IndexError, "index out of range");
+			PyErr_Format(PyExc_IndexError,
+			             "index out of range: %zd", revnum);
 			goto bail;
 		}
 		revs[i] = revnum;