Don't use count as a positional argument in re.sub

This is deprecated in Python 3.13 and the warnings break tests

Author: antonio-rojas

src/sage/interfaces/singular.py

@@ -1401,7 +1401,7 @@ def _repr_(self):
             # this is our cue that singular uses `rp` instead of `ip`
             if singular_name_mapping['invlex'] == 'rp' and 'doctest' in str(get_display_manager()):
                 s = re.sub('^(// .*block.* : ordering )rp$', '\\1ip',
-                           s, 0, re.MULTILINE)
+                           s, count=0, flags=re.MULTILINE)
         return s
 
     def __copy__(self):

src/sage/misc/cython.py

@@ -380,7 +380,7 @@ def cython(filename, verbose=0, compile_message=False,
         cython_messages = re.sub(
             "^.*The keyword 'nogil' should appear at the end of the function signature line. "
             "Placing it before 'except' or 'noexcept' will be disallowed in a future version of Cython.\n",
-            "", cython_messages, 0, re.MULTILINE)
+            "", cython_messages, count=0, flags=re.MULTILINE)
 
         sys.stderr.write(cython_messages)
         sys.stderr.flush()

src/sage/rings/ring_extension_morphism.pyx

@@ -461,7 +461,7 @@ cdef class RingExtensionHomomorphism(RingMap):
         if self.base_map() is not None:
             s += "with map on base ring"
             ss = self.base_map()._repr_defn()
-            ss = re.sub('\nwith map on base ring:?$', '', ss, 0, re.MULTILINE)
+            ss = re.sub('\nwith map on base ring:?$', '', ss, count=0, flags=re.MULTILINE)
             if ss != "": s += ":\n" + ss
         if s != "" and s[-1] == "\n":
             s = s[:-1]