...Semantics change in decrypt_message:
After factoring the code to fit my smaller mental capacity I noticed that in
case of _status being one of PEP_PASSPHRASE_REQUIRED,
PEP_PASSPHRASE_FOR_NEW_KEYS_REQUIRED or PEP_WRONG_PASSPHRASE, encrypt_message
went to the pEp_error label but in the end returned PEP_STATUS_OK.
I assume this was not intended. Simplify further, using status in the place
of _status. Nothing seems to break.