The import of a public key fails if a User-ID packet of the key contains characters that are invalid in UTF-8 encoding. I will attach a test key that is issued for "Test Müller" in ISO-8859-15 encoding that reveals this behaviour. "ü" in ISO-8859-15 has a hex value of
0xfc which is not a valid UTF-8 hexcode.
At import, the console shows this stacktrace:
TypeError: malformed UTF-8 character sequence at offset 6
Note that the key can be handled by RNP on the command line, so it is not a problem of the library.
Especially users with quite old keys in their keyring (pre UTF-8-only times) could be affected by this bug.