[3.9] gh-95778: Mention sys.set_int_max_str_digits() in error message (#96874) (#96877)

When ValueError is raised if an integer is larger than the limit,
mention sys.set_int_max_str_digits() in the error message.

(cherry picked from commit e841ffc)

Co-authored-by: Ned Deily <[email protected]>

Author: vstinner

Doc/library/stdtypes.rst

@@ -5277,15 +5277,15 @@ When an operation would exceed the limit, a :exc:`ValueError` is raised:
    >>> _ = int('2' * 5432)
    Traceback (most recent call last):
    ...
-   ValueError: Exceeds the limit (4300) for integer string conversion: value has 5432 digits.
+   ValueError: Exceeds the limit (4300) for integer string conversion: value has 5432 digits; use sys.set_int_max_str_digits() to increase the limit.
    >>> i = int('2' * 4300)
    >>> len(str(i))
    4300
    >>> i_squared = i*i
    >>> len(str(i_squared))
    Traceback (most recent call last):
    ...
-   ValueError: Exceeds the limit (4300) for integer string conversion: value has 8599 digits.
+   ValueError: Exceeds the limit (4300) for integer string conversion: value has 8599 digits; use sys.set_int_max_str_digits() to increase the limit.
    >>> len(hex(i_squared))
    7144
    >>> assert int(hex(i_squared), base=16) == i*i  # Hexadecimal is unlimited.

Misc/NEWS.d/next/Core and Builtins/2022-09-16-19-02-40.gh-issue-95778.cJmnst.rst

@@ -0,0 +1,3 @@
+When :exc:`ValueError` is raised if an integer is larger than the limit,
+mention the :func:`sys.set_int_max_str_digits` function in the error message.
+Patch by Victor Stinner.

Objects/longobject.c

@@ -38,8 +38,8 @@ PyObject *_PyLong_One = NULL;
 #define IS_SMALL_INT(ival) (-NSMALLNEGINTS <= (ival) && (ival) < NSMALLPOSINTS)
 #define IS_SMALL_UINT(ival) ((ival) < NSMALLPOSINTS)
 
-#define _MAX_STR_DIGITS_ERROR_FMT_TO_INT "Exceeds the limit (%d) for integer string conversion: value has %zd digits"
-#define _MAX_STR_DIGITS_ERROR_FMT_TO_STR "Exceeds the limit (%d) for integer string conversion"
+#define _MAX_STR_DIGITS_ERROR_FMT_TO_INT "Exceeds the limit (%d) for integer string conversion: value has %zd digits; use sys.set_int_max_str_digits() to increase the limit"
+#define _MAX_STR_DIGITS_ERROR_FMT_TO_STR "Exceeds the limit (%d) for integer string conversion; use sys.set_int_max_str_digits() to increase the limit"
 
 static PyObject *
 get_small_int(sdigit ival)