python: Update lists of functions returning gpgme_error_t.
python: Update lists of functions returning gpgme_error_t.

* lang/python/gpg/core.py (Context._errorcheck): Add instructions how
to update the list.  Update list.
(Data._errorcheck): Likewise.
(Context.set_engine_info): Simplify.

Signed-off-by: Justus Winter <4d1bd7a5ca1cd26bee0df05b6801a6ce9a22196e@g10code.com>

gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme,gpg/gpgme