Do not override __richcmp__ in Ring morphisms

src/sage/rings/morphism.pyx

@@ -499,7 +499,7 @@ cdef class RingMap_lift(RingMap):
         _slots['S'] = self.S
         return Morphism._extra_slots(self, _slots)
 
-    def __richcmp__(self, other, int op):
+    def _richcmp_(self, other, int op):
         """
         Compare a ring lifting maps ``self`` to ``other``.
 
@@ -940,7 +940,7 @@ cdef class RingHomomorphism_coercion(RingHomomorphism):
         """
         return "Ring Coercion"
 
-    def __richcmp__(self, other, int op):
+    def _richcmp_(self, other, int op):
         """
         Compare a ring coercion morphism ``self`` to ``other``.
 
@@ -1633,7 +1633,7 @@ cdef class RingHomomorphism_cover(RingHomomorphism):
         """
         return self.codomain().defining_ideal()
 
-    def __richcmp__(self, other, int op):
+    def _richcmp_(self, other, int op):
         """
         Compare ``self`` to ``other``.
 
@@ -1830,7 +1830,7 @@ cdef class RingHomomorphism_from_quotient(RingHomomorphism):
         """
         return self.phi
 
-    def __richcmp__(self, other, op):
+    def _richcmp_(self, other, op):
         """
         Compare ``self`` to ``other``.