### Please describe the problem.
Tried adding a removable drive repository through git-annex assistant on Mac, asked to encrypt it, got Internal server error with explanation: unable to determine gcrypt-id of remote

### What steps will reproduce the problem?
current (today's) version of git-annex build for Mountain Lion installed
app launched
default annex initialized, a couple file added
a removable 2GB USB drive (ExFAT) mounted in OS
click Add another repository
choose removable drive
choose to encrypt
a window explaining the need to wait for entropy shows
then we get the Internal server error: unable to determine gcrypt-id of remote

### What version of git-annex are you using? On what operating system?
git-annex version 4.20130922-g7dc188a
Mac OS X 10.8.5

### Please provide any additional information below.

looking at transcript below, it appears the root cause is the lack of initial git/gcrypt configuration. perhaps this needs to be caught/addressed somehow

[[!format sh """
# If you can, paste a complete transcript of the problem occurring here.
# If the problem is with the git-annex assistant, paste in .git/annex/daemon.log

gpg: can't open `/usr/local/share/gnupg/options.skel': No such file or directory
.......+++++
.+++++
gpg: key 71BFBC31 marked as ultimately trusted
ok
(Recording state in git...)
(Recording state in git...)
(encryption setup) (hybrid cipher with gpg key C4B2EA8D71BFBC31) gcrypt: Development version -- Repository format MAY CHANGE
gpg: checking the trustdb
gpg: 3 marginal(s) needed, 1 complete(s) needed, PGP trust model
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
gcrypt: WARNING: Skipping missing key C4B2EA8D71BFBC31
gcrypt: You have not configured any keys you can encrypt to for this repository
gcrypt: Use ::
gcrypt:   git config gcrypt.participants YOURKEYID
gcrypt: Development version -- Repository format MAY CHANGE
gcrypt: WARNING: Skipping missing key C4B2EA8D71BFBC31
gcrypt: You have not configured any keys you can encrypt to for this repository
gcrypt: Use ::
gcrypt:   git config gcrypt.participants YOURKEYID
03/Oct/2013:00:05:24 +0400 [Error#yesod-core] unable to determine gcrypt-id of remote @(yesod-core-1.1.8.3:Yesod.Internal.Core ./Yesod/Internal/Core.hs:550:5)


# End of transcript or log.
"""]]

[[!tag moreinfo]]