trac 29923: remove use of sage-cython in main sage script,

deprecate all use of sage-cython.

src/bin/sage

@@ -548,7 +548,7 @@ fi
 
 if [ "$1" = "-cython" -o "$1" = '--cython' -o "$1" = '-pyrex' -o "$1" = "--pyrex" ]; then
     shift
-    exec sage-cython "$@"
+    exec cython "$@"
 fi
 
 if [ "$1" = '-gap' -o "$1" = '--gap' ]; then

src/bin/sage-cython

@@ -4,11 +4,15 @@
 # It is deprecated since Trac #27041 (Sage 8.7) because one should
 # simply use "cython" directly. We display deprecation messages whenever
 # "sage-cython" does something different from plain "cython".
+#
+# A stronger deprecation warning was added in #29923 (Sage 9.2).
 
 import os
 import sys
 args = sys.argv[1:]
 
+sys.stderr.write("WARNING: the script sage-cython is deprecated; use cython instead.\n")
+
 from sage.env import SAGE_SRC
 
 # args can have length 0, in case we're printing a usage message (see trac 12207)