bound enum value 0x80000000 raises ValueError: invalid enum value: 2147483648
See gimp#9838 (closed). Describes how to reproduce in Gimp Python Console.
The value has the msb set of 32-bits. The sign bit for signed, twos complement integers.
This line raises the error? when the value is not found in a dictionary.
This comment seems to say it is not tested
Summarizing gimp#9838 (closed) about the importance: it is unlikely any Gimp user would experience this, but it prevents PyCharm from working on the Gimp gir.