Trac #27041: Remove deprecated stuff related to Cython

Remove deprecations from #22698, #22805, #23855, #24105.

Deprecate the script `src/bin/sage-cython`.

URL: https://trac.sagemath.org/27041
Reported by: jdemeyer
Ticket author(s): Jeroen Demeyer
Reviewer(s): Erik Bray

src/bin/sage-cython

@@ -1,5 +1,10 @@
 #!/usr/bin/env python
 
+# This script is a deprecated wrapper around the "cython" program.
+# 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".
+
 import os
 import sys
 args = sys.argv[1:]
@@ -12,24 +17,16 @@ SAGE_SRC = os.environ["SAGE_SRC"]
 pyx_file = os.path.abspath(args[-1]) if len(args) else None
 include_sage_flags = False
 
-if pyx_file and pyx_file.endswith('.spyx'):
-    sys.stderr.write("WARNING: running sage --cython on .spyx files is deprecated, use the .pyx extension instead\n")
-    spyx_file = pyx_file
-    pyx_file = pyx_file[:-5] + '.pyx'
-    args[-1] = pyx_file
-    f = open(pyx_file, 'w')
-    f.write("include 'sage/ext/stdsage.pxi'\ninclude 'sage/ext/cdefs.pxi'\ninclude 'cysignals/signals.pxi'\n\n")
-    f.write(open(spyx_file).read())
-    f.close()
-    include_sage_flags = True
-
 if pyx_file and pyx_file.startswith(SAGE_SRC):
+    sys.stderr.write("WARNING: in the future, sage --cython will not add special flags for files in Sage sources.\n")
     include_sage_flags = True
 
 if '-sage' in args:
+    sys.stderr.write("WARNING: sage --cython -sage is deprecated.\n")
     include_sage_flags = True
     args.remove('-sage')
 elif '-no-sage' in args:
+    sys.stderr.write("WARNING: sage --cython -no-sage is deprecated, remove the -no-sage flag.\n")
     include_sage_flags = False
     args.remove('-no-sage')