Recent GPG changes the keyring format and drops support for RFC1991
formatted signatures, breaking our existing tests.
* ch/new-gpg-drops-rfc-1991:
tests: make comment on GPG keyring match the code
tests: squelch noise from GPG machinery set-up
tests: replace binary GPG keyrings with ASCII-armored keys
tests: skip RFC1991 tests for gnupg 2.1
tests: create gpg homedir on the fly