Merge pull request #1 from jepler/warn-bitlength

Improve the diagnostic when the user's circuitpython is too old

Author: jepler

README.rst

@@ -27,7 +27,7 @@ This library depends on:
 * `Adafruit CircuitPython <https://github.com/adafruit/circuitpython>`_
 
 Note that some CircuitPython core changes were needed to support udecimal.
-These will be in upcoming release 6.0.0.alpha-4.
+Please use CircuitPython 6.0.0-rc.1 or newer with udecimal.
 
 The library also runs on desktop Python3, and should give numerically identical
 results across all platorms.

jepler_udecimal/__init__.py

@@ -160,6 +160,11 @@
 
 if sys.implementation.name == "circuitpython":
 
+    if not hasattr(int, "bit_length"):
+        raise ImportError(
+            "jepler_udecimal requires int.bit_length.  Use CircuitPython 6.0.0-rc.1 or newer."
+        )
+
     def _as_integer_ratio(f):
         m, e = _math.frexp(f)
         m = round(m * (1 << 53))