sagemathgh-36488: Fix func_persist: do not use the (now removed) insp…

…ect.formatargspec, but instead use inspect.signature.

    
Fix func_persist: do not use inspect.formatargspec (gone as of Python
3.11)

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The method `inspect.formatargspec` has been deprecated since Python 3.5,
now removed as of 3.11. `func_persist` still uses it, so we replace it
with `inspect.signature`.

Another option would be to replace it with
`sageinspect.sage_formatargspec`. I think that func_persist should only
be used with Python functions, not Cython, and `inspect.signature` is
nicer for Python functions. If the function is defined as `def test(n:
int) -> int:`, For example, then `inspect.signature` will return `(n:
int) -> int` while `sageinspect.sage_formatargspec` will just return
`(n)`.

This should fix sagemath#36302.

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URL: sagemath#36488
Reported by: John H. Palmieri
Reviewer(s): balejk

src/sage/misc/func_persist.py

@@ -45,7 +45,6 @@ def bern(n):
 
 from . import persist
 
-
 class func_persist:
     r"""
     Put ``@func_persist`` right before your function
@@ -57,7 +56,7 @@ def __init__(self, f, dir='func_persist'):
         os.makedirs(dir, exist_ok=True)
         self.__doc__ = '%s%s%s' % (
             f.__name__,
-            inspect.formatargspec(*inspect.getargs(f.__code__)),
+            inspect.signature(f),
             f.__doc__)
 
     def __call__(self, *args, **kwds):