sq cert import autocrypt-header's output is misleading
When importing an autocrypt header, I got an unusual message "Decryption of message failed." It's unclear to me why we need to decrypt the header. FWIW, importing seems to work, but unlike when I import an OpenPGP certificate, I'm not shown any information about what I imported:
```
$ sq cert import /tmp/patrick.txt
Note: Decryption of message failed: Decryption failed
Imported 1 new certificate, updated 0 certificates, 0 certificates unchanged, 0 errors.
$ sq cert list
- 2C57F8DD637F5DFD6454E625E07F1BF33FB80A1A
- [ ✓ ] Local Trust Root
- 4F9F89F5505AC1D1A260631CDB1187B9DD5F693B
- created 2015-01-17 14:57:05 UTC
- will expire 2025-01-14T14:58:58Z
- [ 40/120 ] Patrick Brunschwig <patrick@enigmail.net>
- EADA8FDA0E05A6BF343326CAB99A02B3CF78CCEB
- [ 40/120 ] Imported from Autocrypt
Hint: To view why a user ID is considered valid, pass `--show-paths`.
Hint: To see more details about a certificate, for example EADA8FDA0E05A6BF343326CAB99A02B3CF78CCEB, run:
$ sq inspect --cert=EADA8FDA0E05A6BF343326CAB99A02B3CF78CCEB
$ sq cert import ~/neal.asc
Imported 8F17777118A33DDA9BA48E62AACB3243630052D9, Neal H. Walfield <neal@walfield.org> (UNAUTHENTICATED)
Imported 1 new certificate, updated 0 certificates, 0 certificates unchanged, 0 errors.
```
[patrick.txt](/uploads/4c93507c2be0ad226daf8426141591f6/patrick.txt)
issue