Trying to instantiate an enum with an invalid value results in "During handling of the above exception, another exception occurred:".


$ cat > test.py << EOF
from enum import Enum

class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

Color(0)
EOF


$ python --version
Python 3.8.1


$ python test.py
ValueError: 0 is not a valid Color

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "test.py", line 8, in <module>
    Color(0)
  File "/usr/lib/python3.8/enum.py", line 304, in __call__
    return cls.__new__(cls, value)
  File "/usr/lib/python3.8/enum.py", line 595, in __new__
    raise exc
  File "/usr/lib/python3.8/enum.py", line 579, in __new__
    result = cls._missing_(value)
  File "/usr/lib/python3.8/enum.py", line 608, in _missing_
    raise ValueError("%r is not a valid %s" % (value, cls.__name__))
ValueError: 0 is not a valid Color


I think this might be related to 019f0a0cb85e ("bpo-34536: raise error for invalid _missing_ results (GH-9147)"), but I haven't been able to confirm.

I can't reproduce this on the latest python (3.9) from master. Can you?

Never mind, I was able to reproduce it.

New changeset c95ad7a91fbd7636f33a098d3b39964ab083bf49 by Ethan Furman in branch 'master':
bpo-39728: Enum: fix duplicate `ValueError` (GH-22277)
https://github.com/python/cpython/commit/c95ad7a91fbd7636f33a098d3b39964ab083bf49

New changeset a9ba8ba9a71f3cb8d274c354ff67b6206abeb8ac by Ethan Furman in branch '3.9':
[3.9] bpo-39728: Enum: fix duplicate `ValueError` (GH-22277) (GH-22282)
https://github.com/python/cpython/commit/a9ba8ba9a71f3cb8d274c354ff67b6206abeb8ac

New changeset 5efb1a77e75648012f8b52960c8637fc296a5c6d by Ethan Furman in branch '3.8':
[3.8] bpo-39728: Enum: fix duplicate `ValueError` (GH-22277) (GH-22283)
https://github.com/python/cpython/commit/5efb1a77e75648012f8b52960c8637fc296a5c6d