remove cached_property def

CHANGELOG-unreleased.md

@@ -15,4 +15,4 @@ the released changes.
 ### Fixed
 - Made `TimingModel.is_binary()` more robust. 
 ### Removed
-
+- Unnecessary definition of `cached_property` from `pint.fitter` (Python 3.8 no longer needs to be supported).

src/pint/fitter.py

@@ -61,6 +61,7 @@
 import contextlib
 import copy
 from warnings import warn
+from functools import cached_property
 
 import astropy.units as u
 import numpy as np
@@ -115,64 +116,6 @@
     "MaxiterReached",
 ]
 
-try:
-    from functools import cached_property
-except ImportError:
-    # not supported in python 3.7
-    # This is just the code from python 3.8
-    from _thread import RLock
-
-    _NOT_FOUND = object()
-
-    class cached_property:
-        def __init__(self, func):
-            self.func = func
-            self.attrname = None
-            self.__doc__ = func.__doc__
-            self.lock = RLock()
-
-        def __set_name__(self, owner, name):
-            if self.attrname is None:
-                self.attrname = name
-            elif name != self.attrname:
-                raise TypeError(
-                    "Cannot assign the same cached_property to two different names "
-                    f"({self.attrname!r} and {name!r})."
-                )
-
-        def __get__(self, instance, owner=None):
-            if instance is None:
-                return self
-            if self.attrname is None:
-                raise TypeError(
-                    "Cannot use cached_property instance without calling __set_name__ on it."
-                )
-            try:
-                cache = instance.__dict__
-            except AttributeError:
-                # not all objects have __dict__ (e.g. class defines slots)
-                msg = (
-                    f"No '__dict__' attribute on {type(instance).__name__!r} "
-                    f"instance to cache {self.attrname!r} property."
-                )
-                raise TypeError(msg) from None
-            val = cache.get(self.attrname, _NOT_FOUND)
-            if val is _NOT_FOUND:
-                with self.lock:
-                    # check if another thread filled cache while we awaited lock
-                    val = cache.get(self.attrname, _NOT_FOUND)
-                    if val is _NOT_FOUND:
-                        val = self.func(instance)
-                        try:
-                            cache[self.attrname] = val
-                        except TypeError:
-                            msg = (
-                                f"The '__dict__' attribute on {type(instance).__name__!r} instance "
-                                f"does not support item assignment for caching {self.attrname!r} property."
-                            )
-                            raise TypeError(msg) from None
-            return val
-
 
 class Fitter:
     """Base class for objects encapsulating fitting problems.