gh-35792: cleaning some things remaining from python 2
    
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### 📚 Description

this is making some little changes, both in code and doc, related to the
transition py2 to py3

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- [ ] I have created tests covering the changes.
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URL: #35792
Reported by: Frédéric Chapoton
Reviewer(s): Matthias Köppe

Author: Release Manager

src/doc/fr/tutorial/afterword.rst

@@ -112,12 +112,12 @@ Aussi, Sage se comporte différemment de Python à plusieurs égards.
         sage: a
         10
 
--  **Division entière :** L'expression Python ``2/3`` ne se comporte pas
-   de la manière à laquelle s'attendraient des mathématiciens. En Python 2, si
-   ``m`` et ``n`` sont de type int, alors ``m/n`` est aussi de type int, c'est
-   le quotient entier de ``m`` par ``n``. Par conséquent, ``2/3=0``. Ce
-   comportement est différent en Python 3, où ``2/3`` renvoie un flottant
-   ``0.6666...`` et c'est ``2//3`` qui renvoie ``0``.
+- **Division entière :** L'expression Python ``2/3`` ne se comporte
+   pas de la manière à laquelle s'attendraient des mathématiciens. En
+   Python 3, si ``m`` et ``n`` sont de type ``int``, alors ``m/n`` est
+   de type ``float``, c'est le quotient réel de ``m`` par ``n``. Par
+   exemple, ``2/3`` renvoie ``0.6666...``. Pour obtenir le quotient
+   entier, il faut utiliser ``2//3`` qui renvoie ``0``.
 
    Dans l'interpréteur Sage, nous réglons cela en encapsulant
    automatiquement les entiers litéraux par ``Integer( )`` et en faisant

src/sage/combinat/tutorial.py

@@ -1048,7 +1048,7 @@
 the function ``sum`` receives the iterator directly, and can
 short-circuit the construction of the intermediate list. If there are a
 large number of elements, this avoids allocating a large quantity of
-memory to fill a list which will be immediately destroyed [2]_.
+memory to fill a list which will be immediately destroyed.
 
 Most functions that take a list of elements as input will also accept
 an iterator (or an iterable) instead. To begin with, one can obtain the
@@ -1805,7 +1805,7 @@
 then the graphs with two edges, and so on. The set of children of a
 graph `G` can be constructed by *augmentation*, adding an edge in all
 the possible ways to `G`, and then selecting, from among those graphs,
-the ones that are still canonical [3]_. Recursively, one obtains all
+the ones that are still canonical [2]_. Recursively, one obtains all
 the canonical graphs.
 
 .. figure:: ../../media/prefix-tree-graphs-4.png
@@ -1848,12 +1848,6 @@
    clean up.
 
 .. [2]
-   Technical detail: ``range`` returns an iterator on
-   `\{0,\dots,8\}` while ``range`` returns the corresponding
-   list. Starting in ``Python`` 3.0, ``range`` will behave like ``range``, and
-   ``range`` will no longer be needed.
-
-.. [3]
    In practice, an efficient implementation would exploit the symmetries
    of `G`, i.e., its automorphism group, to reduce the number of
    children to explore, and to reduce the cost of each test of

src/sage/databases/findstat.py

@@ -2095,7 +2095,7 @@ def oeis_search(self, search_size=32, verbose=True):
         if counter >= 4:
             if verbose:
                 print('Searching the OEIS for "%s"' % OEIS_string)
-            return oeis(str(OEIS_string)) # in python 2.7, oeis does not like unicode
+            return oeis(OEIS_string)
 
         if verbose:
             print("Too little information to search the OEIS for this statistic (only %s values given)." % counter)
@@ -2371,7 +2371,7 @@ def submit(self, max_values=FINDSTAT_MAX_SUBMISSION_VALUES):
             sage: s.set_description(u"Möbius")                                  # optional -- internet
             sage: s.submit()                                                    # optional -- webbrowser
         """
-        args = dict()
+        args = {}
         args["OriginalStatistic"] = self.id_str()
         args["Domain"]            = self.domain().id_str()
         args["Values"]            = self.first_terms_str(max_values=max_values)

src/sage/rings/rational.pyx

@@ -4187,7 +4187,7 @@ cdef class Q_to_Z(Map):
 
 cdef class int_to_Q(Morphism):
     r"""
-    A morphism from Python 2 ``int`` to `\QQ`.
+    A morphism from Python 3 ``int`` to `\QQ`.
     """
     def __init__(self):
         """
@@ -4203,57 +4203,6 @@ cdef class int_to_Q(Morphism):
         from . import rational_field
         import sage.categories.homset
         from sage.sets.pythonclass import Set_PythonType
-        Morphism.__init__(self, sage.categories.homset.Hom(Set_PythonType(int), rational_field.QQ))
-
-    cpdef Element _call_(self, a):
-        """
-        Return the image of the morphism on ``a``.
-
-        EXAMPLES::
-
-            sage: f = sage.rings.rational.int_to_Q()
-            sage: f(int(4)) # indirect doctest
-            4
-        """
-        cdef Rational rat
-
-        if type(a) is not int:
-            raise TypeError("must be a Python int object")
-
-        rat = <Rational> Rational.__new__(Rational)
-        mpq_set_si(rat.value, PyInt_AS_LONG(a), 1)
-        return rat
-
-    def _repr_type(self):
-        """
-        Return string that describes the type of morphism.
-
-        EXAMPLES::
-
-            sage: sage.rings.rational.int_to_Q()._repr_type()
-            'Native'
-        """
-        return "Native"
-
-
-cdef class long_to_Q(Morphism):
-    r"""
-    A morphism from Python 2 ``long``/Python 3 ``int`` to `\QQ`.
-    """
-    def __init__(self):
-        """
-        Initialize ``self``.
-
-        EXAMPLES::
-
-            sage: sage.rings.rational.long_to_Q()
-            Native morphism:
-              From: Set of Python objects of class 'int'
-              To:   Rational Field
-        """
-        from . import rational_field
-        import sage.categories.homset
-        from sage.sets.pythonclass import Set_PythonType
         Morphism.__init__(self, sage.categories.homset.Hom(
             Set_PythonType(long), rational_field.QQ))
 
@@ -4263,7 +4212,7 @@ cdef class long_to_Q(Morphism):
 
         EXAMPLES::
 
-            sage: f = sage.rings.rational.long_to_Q()
+            sage: f = sage.rings.rational.int_to_Q()
             sage: f(4^100)
             1606938044258990275541962092341162602522202993782792835301376
         """
@@ -4289,7 +4238,7 @@ cdef class long_to_Q(Morphism):
 
         EXAMPLES::
 
-            sage: sage.rings.rational.long_to_Q()._repr_type()
+            sage: sage.rings.rational.int_to_Q()._repr_type()
             'Native'
         """
         return "Native"

src/sage/rings/rational_field.py

@@ -374,7 +374,7 @@ def _coerce_map_from_(self, S):
         if S is ZZ:
             return rational.Z_to_Q()
         elif S is int:
-            return rational.long_to_Q()
+            return rational.int_to_Q()
         elif ZZ.has_coerce_map_from(S):
             return rational.Z_to_Q() * ZZ._internal_coerce_map_from(S)
         from sage.rings.localization import Localization

src/sage/structure/sage_object.pyx

@@ -141,7 +141,6 @@ cdef class SageObject:
         if hasattr(self, '__custom_name'):
             del self.__custom_name
 
-
     def __repr__(self):
         """
         Default method for string representation.
@@ -191,11 +190,7 @@ cdef class SageObject:
             reprfunc = self._repr_
         except AttributeError:
             return super().__repr__()
-        result = reprfunc()
-        if isinstance(result, str):
-            return result
-        # Allow _repr_ to return unicode on Python 2
-        return result.encode('utf-8')
+        return reprfunc()
 
     def _ascii_art_(self):
         r"""