python: overhaul logic of Context.decrypt()
* lang/python/src/core.py (Context.decrypt): simplify and clarify the logic behind handling verify=False. * lang/python/tests/t-decrypt.py: ensure that we test verify=False
The function-internal variables were pretty unclear to the reader, and
the logic caused pretty nasty breakage when verify=False.
- GnuPG-Bug-Id: T4271
- Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>