gpg-agent spamming syslog

[Bob Brewer <debian-user@grantura.co.uk>]

I'm running up-to-date Debian Sid and since gnupg-agent was upgraded from 
gnupg-agent:amd64 (2.1.17-3), I have been seeing the following error in 
syslog:

gpg-agent[7545]: can't connect to the SCdaemon: IPC connect call failed

this is repeated every 2 seconds.

I have tried killing gpg-agent with gpgconf --kill gpg-agent but it 
immediately restarts presumably called by systemd but I can't find any 
config files associated with gpg-agent to see where scdaemon is being 
called. scdaemon isn't installed.

Any suggestions where to look for the cause of the syslog error and prevent 
my SSD from being worn out?

Thankyou

Rob


-- System Information:
Debian Release: 9.0
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'testing'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.9.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gnupg-agent depends on:
ii  libassuan0                  2.4.3-2
ii  libc6                       2.24-9
ii  libgcrypt20                 1.7.6-1
ii  libgpg-error0               1.26-2
ii  libnpth0                    1.3-1
ii  libreadline7                7.0-2
ii  pinentry-gnome3 [pinentry]  1.0.0-1
ii  pinentry-gtk2 [pinentry]    1.0.0-1

Versions of packages gnupg-agent recommends:
ii  gnupg  2.1.18-3
ii  gpgsm  2.1.18-3

Versions of packages gnupg-agent suggests:
ii  dbus-user-session  1.10.14-1
ii  libpam-systemd     232-14
ii  pinentry-gnome3    1.0.0-1
pn  scdaemon           <none>

-- no debconf information