Notably verifymessage and decrypt(message) were silently ignoring trailing garbage
or inserted non-base64 characters present in signatures/ciphertext.
(both the CLI commands and in the GUI)
I think it is much cleaner and preferable to treat such signatures/ciphertext as invalid.
In fact I find it surprising that base64.b64decode(validate=False) is the default.
Perhaps we should create a helper function for it that set validate=True and use that.
3e4601c61d
