Bug#369940: libc6 upgrade objects to my old a.out libc in /usr/local

[sysadmin@chiark.greenend.org.uk (Ian Jackson)]

Package: libc6
Version: 2.3.2.ds1-22sarge3

 Preparing to replace libc6 2.3.2.ds1-22 (using .../libc6_2.3.2.ds1-22sarge3_i386.deb) ...
 These libraries were found in /usr/local/lib:
 libc.so.2
 libc.so.2.2
 libm.so.2
 libm.so.2.2

 A copy of glibc was found in an unexpected directory.
 It is not safe to upgrade the C library in this situation;
 please remove that copy of the C library and try again.
 dpkg: error processing
 debian/pool/main/g/glibc/libc6_2.3.2.ds1-22sarge3_i386.deb (--install):
  subprocess pre-installation script returned error exit status 1

...

-chiark:~> file /usr/local/lib/libc.so.2.2
/usr/local/lib/libc.so.2.2: Linux/i386 demand-paged executable (ZMAGIC), stripped
-chiark:~>

What exactly is the problem here ?

Ian.