I need an non-interactive, symetric, passphrase mechanism that can be used on machines beyond my sys-admin control.
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Currently, I use the Python code (with variants):
Stat, Output = commands.getstatusoutput(
"gpg -c --passphrase=%s '%s'"%(Password, TarFileName))
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to encrypt and decrypt files (tar balls). The "Password" is generated by a Python code on a singular removable flash drive. It worked with FC11 and Windows, but with FC13 I get an interactive dialog, which gets canceled, and then:
can't connect to `/home/{a user id}/.gnupg/S.gpg-agent': No such file or directory
gpg-agent[3432]: command get_passphrase failed: Operation cancelled
gpg: cancelled by user
gpg: error creating passphrase: Operation cancelled
gpg: symmetric encryption of `testdata' failed: Operation cancelled
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The operator does not know the pass phrase. This is a single user mechanism which relies upon the mounting of the special flash drive to work. The application is portable across many platforms and hosts, but can only be used by the possessor of the flash drive.

It looks like somewhere in your upgrade process that GPG got reconfigured to use the default keyring, which will be under the home directory of the active user. As you wish to keep the keys on a USB stick, this won't be the case. You either need to edit gpg.conf to tell it to use the USB mounted keyring or in your script set the environment variable telling the system where to find the keyring.